| 1. |
- Blid, Jan, et al.
(författare)
-
Lewis Acid Mediated [2,3]-Sigmatropic Rearrangement of Allylic alpha-Amino Amides
- 2004
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 69:9, s. 3043-3049
-
Tidskriftsartikel (refereegranskat)abstract
- Boron trifluoride and BBr3 mediated [2,3]-sigmatropic rearrangements of allylic alpha-amino amides have been developed affording secondary amines in good yields. (E)-Crotyl and (E)-cinnamyl alpha-amino amides 2b and 2c exhibit excellent syn-diastereoselectivity upon rearrangement with either Lewis acid. The allylic amine 2a forms upon treatment with BF3 or BBr3 a five-membered heterocylic complex in which a single halide anion has been displaced by the carbonyl oxygen atom. The structures of the Lewis acid-amine complexes were elucidated using NMR spectroscopy. A plausible reaction mechanism, based on DFT calculations, is presented. Thus, BF3- or BBr3-complexed allylic amines 2 are shown to preferentially proceed, after deprotonation, via an endo transition state.
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| 2. |
- Blid, Jan, 1970-
(författare)
-
Asymmetric [2,3]-Sigmatropic Rearrangement of Allylic Ammonium Ylides
- 2005
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The thesis describes the realization of an asymmetric [2,3]-sigmatropic rearrangement of achiral allylic amines. It is divided into two parts; the first part deals with the development of a Lewis acid-mediated [2,3]-sigmatropic rearrangement and the second the asymmetric version thereof. Quaternization of an -amino amide with various Lewis acids established BBr3 and BF3 to be the most appropriate ones. Various allylic amines were subsequently rearranged into the corresponding homoallylic amines in good to excellent syn-diastereoselectivities, revealing the endo-transition state to be the preferred pathway. The structures of the intermediate Lewis acid-amine complexes were confirmed by NMR spectroscopy studies and DFT calculations. Based on this investigation a chiral diazaborolidine was chosen as Lewis acid and was shown to efficiently promote the asymmetric [2,3]-sigmatropic rearrangement furnishing homoallylic amines in good yields and excellent enantiomeric excesses. In contrast to the achiral rearrangement mediated by BBr3 and BF3, the asymmetric version gave the opposite major diastereomer, revealing a preference for the exo-transition state in the asymmetric rearrangement. To account for the observed selectivities, a kinetic and thermodynamic pathway was presented. On the basis of a deuterium exchange experiment on a rearranged Lewis acid-amine complex and an NMR spectroscopic investigation, the kinetic pathway was shown to be favored.
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| 3. |
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| 4. |
- Blid, Jan, et al.
(författare)
-
Asymmetric [2,3]-sigmatropic rearrangement of allylic ammonium ylides
- 2005
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 127:26, s. 9352-9353
-
Tidskriftsartikel (refereegranskat)abstract
- An asymmetric Lewis acid-mediated [2,3]-sigmatropic rearrangement of allylic amines has been developed, affording the corresponding homoallylic amines in good yield and excellent enantioselectivities. The rearrangement proceeds by complexation of the chiral Lewis acid to the amine followed by deprotonation and rearrangement.
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| 5. |
- Blid, Jan, et al.
(författare)
-
Lewis Acid Mediated [2,3]-Sigmatropic Rearrangement of Allylic Ammonium Ylides
- 2003
-
Ingår i: Tetrahedron Letters. - 0040-4039 .- 1359-8562. ; 44:15, s. 3159-3162
-
Tidskriftsartikel (refereegranskat)abstract
- An investigation of the Lewis acid mediated [2,3]-sigmatropic rearrangement of allylic ammonium ylides has been conducted by employing various bases and boron Lewis acids. Using BBr3 together with the phosphazene base 6, various allylic amines could be rearranged in good yields with low to excellent diastereoselectivity.
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| 6. |
- Blid, Jan, et al.
(författare)
-
Lewis acid mediated asymmetric 2,3 -sigmatropic rearrangement of allylic amines. Scope and mechanistic investigation
- 2007
-
Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 72:4, s. 1294-1300
-
Tidskriftsartikel (refereegranskat)abstract
- [GRAPHIC] The first asymmetric [2,3]-sigmatropic rearrangement of achiral allylic amines has been realized by quaternization of the amines with an enantiomerically pure diazaborolidine and subsequent treatment with Et3N. The resultant homoallylic amines were obtained in good yields and excellent ee's. The observed diastereo- and enantioselectivities were rationalized by invoking a kinetically controlled process, and support for this model was obtained from an NMR spectroscopic investigation of the chiral Lewis acid-substrate complex. The structure of the Lewis acid-product complex was established by X-ray crystallographic analysis and supported the proposed mechanism.
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| 7. |
- Borg, Tessie, et al.
(författare)
-
Diastereoselective formation of 2,3,4,5-tetrasubstituted tetrahydrofurans by a Lewis acid promoted addition of C3-substituted 1,3-bis(silyl)propenes to aldehydes
- 2013
-
Ingår i: Tetrahedron Letters. - : Pergamon Press. - 0040-4039 .- 1359-8562. ; 54:30, s. 3916-3918
-
Tidskriftsartikel (refereegranskat)abstract
- A mild, efficient, Lewis acid promoted addition of C3-substituted 1,3-bis(silyl)propenes to aldehydes to provide the corresponding 2,3,4,5-tetrasubstituted tetrahydrofurans in excellent stereoselectivity is reported.
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| 8. |
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| 9. |
- Borg, Tessie, et al.
(författare)
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Diastereoselective Nucleophilic Addition to Aldehydes with Polar alpha- and alpha,beta-Substituents
- 2011
-
Ingår i: Advanced Synthesis and Catalysis. - : Wiley. - 1615-4150 .- 1615-4169. ; 353:11-12, s. 2022-2036
-
Tidskriftsartikel (refereegranskat)abstract
- The stereoselectivities obtained in Lewis acid-promoted Mukaiyama aldol additions and Sakurai allylations of mono-, and syn- and anti-disubstituted aldehydes possessing various polar alpha- and beta-substituents under non-chelating conditions are presented. The stereochemical outcome in the nucleophilic addition to alpha-substituted aldehydes containing an alpha-benzyloxy, alpha-fluoro or alpha-sulfonamide substituent are accurately predicted by current stereoinduction models. In contrast, the selectivitites obtained from addition of sterically demanding nucleophiles to alpha-chloro-substituted aldehydes cannot be rationalized by the same models and an alternative is discussed. The stereochemichal outcome in the additions to alpha, beta-disubstituted aldehydes is more complex and cannot be predicted using current models.
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| 10. |
- Borg, Tessie, et al.
(författare)
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Lewis Acid-Promoted Addition of 1,3-Bis(silyl)propenes to Aldehydes : A Route to 1,3-Dienes
- 2011
-
Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 76:19, s. 8070-8075
-
Tidskriftsartikel (refereegranskat)abstract
- The Lewis acid-promoted addition of 1,3-bis(silyl)-propenes to aldehydes to provide the corresponding (E)-1,3-dienes in excellent stereoselectivity and good to excellent yields is reported. The procedure is mild, base-free, and operationally straightforward.
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| 11. |
- Borg, Tessie, et al.
(författare)
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Mukaiyama aldol addition to α-chloro-substituted aldehydes. Origin of the unexpected syn selectivity.
- 2010
-
Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 46:8, s. 1281-1283
-
Tidskriftsartikel (refereegranskat)abstract
- The addition of sterically demanding enolsilanes to alpha-chloro aldehydes results unexpectedly in preferential formation of the anti-PFA product (1,2-syn), while the addition of the corresponding boron enolate furnishes the expected polar Felkin-Anh product (1,2-anti). A stereoinduction model explaining these observations is proposed.
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| 12. |
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| 13. |
- Danielsson, Jakob, et al.
(författare)
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1,3-Dipolar Cycloaddition of Azomethine Ylides to Aldehydes : Synthesis of anti alpha-Amino-beta-Hydroxy Esters
- 2011
-
Ingår i: European Journal of Organic Chemistry. - : Wiley. - 1434-193X .- 1099-0690. ; :3, s. 607-613
-
Tidskriftsartikel (refereegranskat)abstract
- A 1,3-dipolar cycloaddition reaction of azomethine ylides to aldehydes is described. The azomethine ylides, generated by thermal electrocyclic ring opening of aziridines, adds to aldehydes in good yields with moderate to good selectivities to furnish oxazolidines. The oxazolidines were subsequently hydrolyzed to the corresponding amino alcohols, giving the anti diastereomer as the major product.
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| 14. |
- Danielsson, Jakob, 1985-
(författare)
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Stereoselective Nucleophilic Additions to Aldehydes and Synthesis of α-Amino-β- Hydroxy-Esters
- 2012
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with the development of new reaction methodology as well as stereochemical investigations. The first part concerns the investigation of 1,2- and merged 1,2- and 1,3- asymmetric induction in Mukaiyama aldol additions to α-heteroatom and α,β- heteroatom substituted aldehydes respectively. In particular, the unexpected 1,2-syn selectivity obtained in the addition of sterically hindered nucleophiles to α-chloroaldehydes is examined, and an explanation for the observed stereochemical trends is proposed. The second part describes the development of a novel entry to α-amino-β- hydroxy esters by a 1,3-dipolar cycloaddition reaction of aldehydes and azomethine ylides, generated by thermolysis of aziridines. The third part deals with our efforts to develop a novel entry to vicinal all- carbon quaternary centers, based on an intramolecular domino Heck- carbonylation reaction using tetrasubstituted olefins.
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| 15. |
- Danielsson, Jakob, et al.
(författare)
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Studies Toward Communesin F: A Diels-Alder Approach.
- 2014
-
Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7052 .- 1523-7060. ; 16:3, s. 784-787
-
Tidskriftsartikel (refereegranskat)abstract
- A Diels-Alder reaction is used as a key step in a synthetic study toward communesin F, in order to simultaneously introduce both of the all-carbon quaternary stereocenters with complete control of relative stereochemistry. Further manipulations of the cycloadduct, toward the hexacyclic core-structure of communesin F, are also disclosed.
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| 16. |
- Danielsson, Jakob, et al.
(författare)
-
Total Synthesis of Dehaloperophoramidine : Evolution of a Synthesis
- 2017
-
Ingår i: Strategies and Tactics in Organic Synthesis. - 1874-6004. ; 13, s. 217-242
-
Bokkapitel (refereegranskat)abstract
- This account describes our efforts toward developing a stereodivergent entry to perophoramidine and the communesin alkaloids. The original approach toward our simplified model substrates relied on a palladium-catalyzed carbopalladation–carbonylation of a tetrasubstituted olefin to install the vicinal all-carbon quaternary stereocenters present in the target molecules, the olefin's stereochemistry thus dictating the relative stereochemistry of the quaternary stereocenters. Although the carbonylation–carbopalladation sequence worked well for trisubstituted olefins, only premature esterification was observed when using tetrasubstituted alkene substrates. Our second approach made use of the latent symmetry embedded in our target molecules. A Diels–Alder reaction or SmI2-mediated bis-alkylation of isoindigo was to be used to access the communesin and perophoramidine scaffolds, respectively. We found that due to unfavorable thermodynamics, it was not possible to reach the communesin scaffold. However, two new complexity-generating, cascade reactions were encountered en route to the synthesis of dehaloperophoramidine, resulting in a short and efficient synthesis.
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| 17. |
- Dressel, Martina, et al.
(författare)
-
Total synthesis of (+)-alexine by utilizing a highly stereoselective 3+2 annulation reaction of an N-tosyl-alpha-amino aldehyde and a 1,3-bis(silyl)propene
- 2008
-
Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 14:10, s. 3072-3077
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Tidskriftsartikel (refereegranskat)abstract
- A novel route towards the polyhydroxylated pyrrolizidine alkaloid (+)-alexine has been developed. A key step in this synthesis is a highly stereoselective [3+2] annulation reaction of N-Ts-alpha-amino aldehyde 7a (Ts=tosyl) and 1,3-bis(silyl)propene 8a for the construction of the polyhydroxylated pyrrolidine subunit of the target molecule. Previous synthetic strategies rely on carbohydrates that require several protecting-group manipulations, thereby making the total number of steps relatively high. The [3+2] annulation strategy compares favorably with carbohydrate-based syntheses and constitutes a highly efficient entry to polyhydroxylated alkaloids.
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| 18. |
- Hirner, Sebastian, et al.
(författare)
-
Microwave-Assisted Rearrangement of Vinylaziridines to 3-Pyrrolines : Formal Synthesis of (-)-Anisomycin
- 2005
-
Ingår i: Synlett. - : Georg Thieme Verlag KG. - 0936-5214 .- 1437-2096. ; :20, s. 3099-3102
-
Tidskriftsartikel (refereegranskat)abstract
- An efficient microwave-assisted rearrangement of activated vinylaziridines to 3-pyrrolines is described. The rearrangement proceeds in good to excellent yields and is mediated by NaI or LiI in MeCN at elevated temperatures. The synthetic utility of this reaction is shown in an efficient formal total synthesis of the antibiotic (-)-anisomycin.
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| 19. |
- Hirner, Sebastian, 1979-
(författare)
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New Methodologies in Organic Chemistry: Applications to the Synthesis of α-Amino Acids and Natural Products
- 2009
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with the development and application of new synthetic methodology in organic chemistry. The first part describes the development of a new protocol for the synthesis of 3-pyrrolines by means of a microwave-assisted ring-expansion reaction of 2-vinylaziridines. In addition, this methodology is implemented as a key-step in a formal total synthesis of the antibiotic (-)-anisomycin. In the second part, a new methodology for the synthesis of arylglycines from Weinreb amides is described. In this procedure, a Grignard reagent is added to the iminium ion formed from the Weinreb amide upon treatment with a base. When a chiral amide is used, the nucleophilic addition proceeds with high diastereoselectivity. Finally, an easy and straightforward synthesis of α-amino amides via a base-mediated rearrangement of modified Weinreb amides into N,O-acetals is presented. Subsequent arylation, alkylation, alkenylation or alkynylation of this intermediate affords the corresponding α-amino amides in excellent yields. Furthermore, a more generalized protocol for the α-arylation of Weinreb amides lacking an α-amino moiety is also discussed.
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| 20. |
- Hirner, Sebastian, et al.
(författare)
-
Synthesis of alpha-Amino Acids by Umpolung of Weinreb Amide Enolates
- 2008
-
Ingår i: European Journal of Organic Chemistry. - : Wiley. - 1434-193X .- 1099-0690. ; :33, s. 5583-5589
-
Tidskriftsartikel (refereegranskat)abstract
- An efficient and diastereoselective synthesis of alpha-amino acids from readily available starting materials has been developed. The key feature of this reaction is an umpolung of a glycine-derived enolate, providing an alternative approach for the synthesis of alpha-amino acids.
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| 21. |
- Hirner, Sebastian, et al.
(författare)
-
Synthesis of alpha-Amino Amides via N,O-Acetals Derived from Weinreb Amides
- 2009
-
Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 74:20, s. 7798-7803
-
Tidskriftsartikel (refereegranskat)abstract
- An easy and straightforward synthesis of alpha-amino amides via a base-mediated rearrangement of modified Weinreb amides into N,O-acetals is presented. Subsequent arylation, alkylation, alkenylation, or alkynylation of this intermediate affords the corresponding alpha-amino amides in excellent yields. Furthermore, a more generalized protocol for the alpha-arylation of Weinreb amides lacking an alpha-amino moiety is also discussed.
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| 22. |
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| 23. |
- Hoang, Anita, et al.
(författare)
-
An Efficient Synthesis of (±)-Dehaloperophoramidine
- 2017
-
Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 82:4, s. 2171-2176
-
Tidskriftsartikel (refereegranskat)abstract
- Perophoramidine and communesin F are structurally related indole alkaloids with an intriguing polycyclic core containing vicinal all-carbon quaternary stereocenters. Dehaloperophoramidine is a dehalogenated synthetic analogue of perophoramidine. Synthetic studies toward the total synthesis of dehaloperophoramidine have led to the discovery of two novel domino processes, the first encompassing four steps and resulting in the formation of an ortho-amide. A thorough study of the reactivity of the ortho-amide functionality revealed the second domino reaction and ultimately yielded the target molecule. The vicinal all-carbon quaternary stereocenters having trans relative stereochemistry are constructed early in the reaction sequence by employing Overman's samarium mediated reductive dialkylation procedure. Described are the synthetic studies that led to the final eight-step synthesis of dehaloperophoramidine.
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| 24. |
- Hussenius, Anita, 1956-, et al.
(författare)
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Kinetic study of a homodienyl-[1,5]-hydrogen shift in a vinylzaziridine
- 1996
-
Ingår i: Journal of Physical Organic Chemistry. - : JOHN WILEY & SONS LTD. - 0894-3230 .- 1099-1395. ; 9:9, s. 623-625
-
Tidskriftsartikel (refereegranskat)abstract
- The thermal rearrangement of an N-substituted vinylaziridine to the corresponding (Z)-allylic imine, i.e. a homodienyl-[1,5]-hydrogen shift, was studied at different temperatures in the range 40-90 degrees C. H-1 NMR spectroscopy was used to follow the r
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| 25. |
- Lindén, Auri, 1975-
(författare)
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Flavins as Biomimetic Catalysts for Sulfoxidation by H2O2 : Catalyst Immobilization in Ionic Liquid for H2O2 Oxidations
- 2005
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with the development of catalytic oxidation reactions utilizing hydrogen peroxide as terminal oxidant. The main focus has been to find flavin catalysts that are easy to handle and stable to store but still able to perform the desired reaction. A variety of dihydroflavins were prepared and the electrochemical oxidation potentials were measured and compared with their catalytic activity.A flavin catalyst was applied in the sulfoxidation of allylic and vinylic sulfides by H2O2. This transformation was highly chemoselective and the sulfoxides were obtained without formation of other oxidation products. The scope of the reaction was demonstrated by applying the method on substrates with a wide range of functional groups such as a tertiary amine. Another flavin catalyst was immobilized in the ionic liquid [BMIm]PF6 and used for sulfoxidations by H2O2. The chemoselectivity was maintained in this system and the catalyst-ionic liquid system could be recycled several times.Finally two bimetallic catalyst systems for the dihydroxylation of alkenes by H2O2 were immobilized in the ionic liquid. These systems employed either vanadium acetylacetonate VO(acac)2 or methyl trioxorhenium (MTO) as co-catalysts together with the substrate-selective osmium catalyst. Good to excellent yields of the diols were obtained.
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| 26. |
- Lindquist, Charlotta, et al.
(författare)
-
Microwave-Assisted Coupling of Carboxylic Acids to a Polymer Bound Hydrazine Linker
- 2003
-
Ingår i: Synthetic Communications. - New York : Marcel Dekker, Inc.. - 0039-7911 .- 1532-2432. ; 33:13, s. 2257-2262
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Tidskriftsartikel (refereegranskat)abstract
- A set of carboxylic acids, all being potential scaffolds for combinatorial chemistry or peptide synthesis, were coupled to a polymer bound aryl hydrazine linker using microwave irradiation in good yields. Improved yields and reduced reaction times were achieved byusing microwave-assisted heating compared to conventional heating.
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| 27. |
- Lindquist, Charlotta, et al.
(författare)
-
Parallel synthesis of an indole-based library via an iterativeMannich reaction sequence
- 2006
-
Ingår i: Tetrahedron. - : Elsevier Ltd.. - 0040-4020 .- 1464-5416. ; 62:14, s. 3439-3445
-
Tidskriftsartikel (refereegranskat)abstract
- A library of 1,3-disubstituted indoles has been prepared via an iterative Mannich reaction sequence. The first Mannich reaction with secondary amines and formaldehyde preferentially yields 3-aminomethyl indoles, while the second Mannich reaction introduces an additional aminomethyl group at the N1-position of the indole ring. A library of 25 substituted indoles has thus been prepared in moderate to good yields with purity.
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| 28. |
- Lindström, U. M., et al.
(författare)
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Aza- 3,3 -claisen enolate rearrangement in vinylaziridines : Stereoselective synthesis of mono-, di-, and trisubstituted seven-membered lactams
- 2001
-
Ingår i: Chemistry - A European Journal. - 0947-6539 .- 1521-3765. ; 7:1, s. 94-98
-
Tidskriftsartikel (refereegranskat)abstract
- Several 2,3-disubstituted vinylaziridines have been N-acylated and subjected to LiHMDS in THF at - 78 degreesC. Upon warming to room temperature, the resulting amide enolates underwent a highly stereoselective [3,3]-sigmatropic rearrangement to give mono-, di-, and trisubstituted seven-membered lactams in good yields. The scope and limitations of the process have been investigated by using variously substituted vinylaziridines. A kinetically controlled process proceeding through a six-membered boatlike transition state assembly has been invoked to explain the stereochemical outcome of the reaction.
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| 29. |
- Lindström, Ulf M., et al.
(författare)
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Microwave-assisted aminolysis of vinylepoxides
- 1999
-
Ingår i: Tetrahedron Letters. - 0040-4039 .- 1359-8562. ; 40:52, s. 9273-9276
-
Tidskriftsartikel (refereegranskat)abstract
- Di- and trisubstituted vinyl epoxides in NH4OH were subjected to microwave irradn. affording the corresponding vicinal amino alcs. in high yields. The reaction is stereospecific and highly regioselective for addn. at the allylic carbon. [on SciFinder(R)]
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| 30. |
- Mohiti, Maziar, et al.
(författare)
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Regio- and Enantioselective Synthesis of 1,2-Diamines by Formal Hydroamination of Enamines : Scope, Mechanism, and Asymmetric Synthesis of Orthogonally Protected Bis-Piperazines as a Privileged Scaffold
-
Ingår i: Chemistry - A European Journal. - 0947-6539.
-
Tidskriftsartikel (refereegranskat)abstract
- We have previously reported the first formal hydroamination of enamines for the synthesis of chiral 1,2-diamines. Here, we describe: (i) the discovery, optimization, and substrate expansion of this reaction; (ii) a novel and straightforward protocol for the “click-type” synthesis of enamines in quantitative yield utilizing sodium sulfate in a dual role as an ancillary and dehydrating agent without the need for workup or purification; (iii) the application of this methodology to the first enantioselective synthesis of orthogonally protected 1,1′-(1-(4-fluorophenyl)ethane-1,2-diyl) piperazines, a scaffold for rapid lead optimization in drug discovery; (iv) a computational investigation into the mechanism and rationalization of the enantioselectivities of the reaction.
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| 31. |
- Neimert-Andersson, Kristina, et al.
(författare)
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A Metathesis Approach for the Preparation of Polyhydroxylated Compounds as Head Groups in Surfactant Synthesis
- 2006
-
Ingår i: European Journal of Organic Chemistry. - : Wiley. - 1434-193X .- 1099-0690. ; :4, s. 978-985
-
Tidskriftsartikel (refereegranskat)abstract
- Starting from methyl-a-D-glucopyranoside, an efficient protocol for the preparation of polyhydroxylated surfactant head-groups is demonstrated and applied in the synthesis of a typical surfactant. The key transformation is a metathesis reaction between two monosaccharide residues to afford an octahydroxydecen. The importance of a strategic protecting-group constellation for a successful metathesis reaction is also investigated.
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| 32. |
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| 33. |
- Neimert-Andersson, Kristina, et al.
(författare)
-
Stereoselective Synthesis of Polyhydroxyl Surfactants. Stereochemical Influence on Langmuir Monolayers
- 2004
-
Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 69:11, s. 3746-3752
-
Tidskriftsartikel (refereegranskat)abstract
- Herein is described the synthesis of surfactants featuring polyhydroxylated head groups. Three head groups were prepared via consecutive stereoselective dihydroxylations of a diene. By coupling of these with lipophilic tail groups six novel surfactants have been prepared. The monolayers prepared from four of these have been investigated at the air-water interface. Significant differences were observed between monolayers consisting of enantiomerically pure surfactants contra racemates as well as between diastereomers.
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| 34. |
- Neimert-Andersson, Kristina, et al.
(författare)
-
Synthesis of New Sugar-Based Surfactants and Evaluation of their Haemolytic Activities
- 2006
-
Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 71:9, s. 3623-3626
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The synthesis of four sugar-based surfactants derived from glucose and (R)-12-hydroxystearic acid is described. The surfactants have a hydroxy group in the hydrophobic part, which is either free or acylated using acetyl chloride, hexanoyl chloride, or myristoyl chloride. Three of the synthesized surfactants are water-soluble and are evaluated with respect to their CMCs and hemolytic activities. The fourth surfactant has limited water solubility and is not further included in the study. The investigated surfactants are all hemolytic close to their respective CMC indicating that their use in parenteral formulations may be limited. Nevertheless, surfactants having the proposed structure appear as promising alternatives to existing solubilizing agents for pharmaceutical applications.
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| 35. |
- Neimert-Andersson, Kristina
(författare)
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Synthesis of Polyhydroxylated Surfactants : Comparison of Surfactant Stereoisomers and Investigation of Haemolytic Activity
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- I den här avhandlingen har vi studerat hur man kan göra nya tensider. En tensid är en speciell molekyl som har förmågan att lösa sig i både vatten och olja. Man kan göra följande experiment hemma: Fyll en glasburk till hälften med vatten och tillsätt en droppe matolja. Oljan bildar en droppe ovanpå vattnet, därför att vatten och olja inte är blandbara. Vatten är polärt och olja är opolärt. Om man rör om med en sked kommer oljedroppen förvisso att dela upp sig i mindre droppar, men så snart man slutar att röra kommer dessa att lägga sig på vattenytan igen. Sätt nu en droppe diskmedel till blandningen och rör om. Nu sprider sig oljedropparna mycket bättre i vattnet, och de lägger sig heller inte på vattenytan lika fort när man slutar att röra. Det här beror på att diskmedel innehåller en tensid, som har en polär och en opolär del. Den polära delen passar ihop med det polära vattnet, medan den opolära delen passar ihop med den opolära oljan. På så vis kan tensiden hjälpa till att lösa upp opolära ämnen i polära vätskor. Den aktiva delen av ett läkemedel består ofta av opolära ämnen, vilka inte löser sig i polära vätskor såsom vatten. Eftersom kroppen består till stor del av vatten måste man ändå försöka få läkemedlet vattenlösligt, för att möjliggöra transport via blodet till problemområdet. Det kan man uppnå genom att tillsätta tensider. Om läkemedel-tensidblandningen ska ges till djur eller människor får inte tensiden orsaka någon skada i kroppen. Vi har försökt framställa tensider som ska kunna användas för att just lösa läkemedel i vatten. För att kunna framställa nya tensider måste man ha kunskap i organisk syntes. Det betyder att man måste veta hur man från små intermediat (”byggstenar”) successivt kan bygga upp nya molekyler som har de önskvärda egenskaperna. Genom olika typer av organisk syntes har vi byggt upp tre nya tensidtyper, vars egenskaper vi studerat med olika mätningar. Ingen av dessa tensider lämpade sig som tillsats till läkemedel, men vårt arbete har givit mycket ny kunskap om hur framtida tensidmolkyler kan tillverkas och vilka egenskaper de får.
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| 36. |
- Olofsson, Berit, et al.
(författare)
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A regio- and stereodivergent route to all isomers of vic-amino alcohols
- 2002
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 67:24, s. 8574-8583
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Tidskriftsartikel (refereegranskat)abstract
- Vicinal amino alcohols are substructures in several important natural products. They are also frequently employed ligands in asymmetric synthesis. Many enantioselective syntheses of vic-amino alcohols have been reported, but each structure has required its own synthetic route. This study presents a synthetic strategy leading to all eight possible isomers of a given beta-amino alcohol, starting from vinyl epoxides. The developed strategy focuses on the propensity of vinyl epoxides and vinylaziridines to be selectively ring-opened at the allylic position by suitable hard nucleophiles. Within this strategy, a novel large-scale aminolysis reaction and the synthesis of a trisubstituted N-H vinylaziridine are detailed.
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| 37. |
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| 38. |
- Olofsson, Berit, et al.
(författare)
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A regio- and stereodivergent synthesis of vic-amino alcohols
- 2000
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Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7060 .- 1523-7052. ; 2:25, s. 4087-4089
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Tidskriftsartikel (refereegranskat)abstract
- [GRAPHICS] A regio- and stereodivergent synthesis of vic-amino alcohols starting from vinylepoxides is described. The developed strategy focuses on the propensity of vinylepoxides and vinylaziridines to be ring-opened at the allylic position by suitable nucleophiles and makes use of reactions that perform such tasks selectively with either retention or inversion of configuration.
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| 39. |
- Olofsson, Berit, et al.
(författare)
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Determination of the relative configuration of vic-amino alcohols
- 2003
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Ingår i: Tetrahedron Letters. - 0040-4039 .- 1359-8562. ; 44:6, s. 1279-1281
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Tidskriftsartikel (refereegranskat)abstract
- A large set of syn- and anti-1,2-amino alcohols has been synthesized. Upon comparison of the CHO and CHN H-1 NMR shifts a general trend has been observed, making it possible to determine the relative configuration of 1,2-amino alcohols without derivatization or shift reagents.
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| 40. |
- Olofsson, Berit, et al.
(författare)
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Divergent synthesis of D-erythro-sphingosine, L-threo-sphingosine, and their regioisomers
- 2003
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 68:6, s. 2514-2517
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Tidskriftsartikel (refereegranskat)abstract
- Starting from a vinyl epoxide, a divergent synthesis of four sphingosine isomers is described. The remaining four isomers can easily be synthesized using the same methodology. Although numerous syntheses of sphingosine have been published, this is the first general route leading to all eight isomers in this important compound class. The synthetic strategy relies on regioselective opening of a vinyl epoxide and a vinylaziridine in the allylic position.
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| 41. |
- Olofsson, Berit, et al.
(författare)
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Synthesis of N-H vinylaziridines : a comparative study
- 2002
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Ingår i: Tetrahedron. - 0040-4020 .- 1464-5416. ; 58:30, s. 5979-5982
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Tidskriftsartikel (refereegranskat)abstract
- Vinylaziridines are useful and versatile synthetic intermediates, as the relief of ring-strain provides a driving force for efficient ring-opening or ring-expansion reactions. Furthermore, the vinyl group can be derivatized into interesting functionalities. The ring-closure of vicinal amino alcohols constitutes a straightforward route to aziridines. Several methods exist for this transformation, although many cannot be applied to vinylaziridines due to their acid lability. This comparative study describes the most effective sequences for the formation of N-H vinylaziridines.
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| 42. |
- Olofsson, Berit, et al.
(författare)
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Vinylepoxides in Organic Synthesis
- 2006
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Ingår i: Aziridines and Epoxides in Organic Synthesis. - Weinheim, FRG : John Wiley & Sons. - 9783527312139 ; , s. 315-347
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Bokkapitel (refereegranskat)
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| 43. |
- Popov, Kirill, et al.
(författare)
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Concise Total Synthesis of Dehaloperophoramidine.
- 2015
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Ingår i: Angewandte Chemie (International edition). - : Wiley. - 1521-3773.
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Tidskriftsartikel (refereegranskat)abstract
- Perophoramidine, dehaloperophoramidine, and communesin F are structurally related alkaloids having intriguing polycyclic structures. A strategy for the synthesis of dehaloperophoramidine has been developed. In this synthesis all skeletal atoms and all functional groups required to reach the target molecule are incorporated early in the sequence. This approach led to the discovery of two novel substrate-specific domino processes, one encompassing four steps and the other comprising five steps, thus resulting in an eight-step synthesis of dehaloperophoramidine.
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| 44. |
- Popov, Kirill, et al.
(författare)
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Synthesis of Imidates : TFA-Mediated Regioselective Amide Alkylation Using Meerwein's Reagent
- 2016
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 81:8, s. 3470-3472
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Tidskriftsartikel (refereegranskat)abstract
- Regioselective O-alkylation of an amide to form the corresponding imidate is a common synthetic problem, often resulting in varying amounts of N-alkylation. Screening existing methods for converting amides to imidates gave inconsistent or irreproducible results, sometimes affording N-alkylamide as the major product. A simple and reliable protocol for amide O-alkylation with complete regioselectivity has been designed, and its scope and efficiency demonstrated on a number of substrates.
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| 45. |
- Ray, C. A., et al.
(författare)
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Diastereoselective Lewis acid-catalysed 4+2 cycloadditions of 3-alkyl-, 3-aryl- and 3-carboxyl-2H-azirines : a route to aziridine containing azabicyclo 4.1.0 heptanes and azatricyclo 2.2.1.0 nonanes
- 2002
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Ingår i: Tetrahedron. - 0040-4020 .- 1464-5416. ; 58:30, s. 5983-5987
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Tidskriftsartikel (refereegranskat)abstract
- 3-Substituted-2H-azirines have been employed as 2pi components in Lewis acid-catalysed hetero Diels-Alder reactions with a variety of diene systems. A series of Lewis acids were screened for catalytic behaviour in the reaction between Danishefsky's diene and 3-phenyl-2H-azirine to give the cycloaddition adduct, and in most cases elevated temperature were required to effect cycloaddition. A noteworthy exception was a BF3.Et2O-catalysed cycloaddition which proceeded in less than I h between -70degreesC and -60degreesC. The cycloadditions were found to proceed with endo selectivity providing a single diastereoisomeric product. Benzyl 2H-azirine-3-carboxylates were found to be activated by Lewis acids and participate in endo selective cycloadditions at -20degreesC.
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| 46. |
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| 47. |
- Restorp, Per, et al.
(författare)
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Diastereoselective Aldol Additions to α-Amino-β-Silyloxy Aldehydes. Divergent Synthesis of Aminodiols
- 2005
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Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7060 .- 1523-7052. ; 7:5, s. 893-895
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Tidskriftsartikel (refereegranskat)abstract
- A divergent protocol for substrate-controlled diastereoselective synthesis of aminodiols has been developed using nucleophilic Mukaiyama aldol additions to alpha-amino-beta-silyloxy aldehydes. The merged stereochemical impact on the diastereoselectivity of the polar alpha- and beta-substituents is highlighted.
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| 48. |
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| 49. |
- Restorp, Per, et al.
(författare)
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Regioselective and Divergent Opening of Vinyl Epoxides with Alkyne Nucleophiles
- 2005
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Ingår i: European Journal of Organic Chemistry. - : Wiley. - 1434-193X .- 1099-0690. ; 18, s. 3946-3951
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Tidskriftsartikel (refereegranskat)abstract
- A divergent procedure for nucleophilic ring-opening of vinyl epoxides with alkynes has been developed, The combination of lithium acetylides and BF(3)center dot OEt2 afforded the S(N)2 products, whereas alkynylalanes gave S(N)2' addition. The regioselectivity of these processes is affected by the alkyne substituent. Ethoxyacetylene added with complete regiocontrol under both SN2 and SN2' conditions, and the SN2 isomeric adducts could he rearranged into gamma-butyrolactones. The synthetic utility of the process is demonstrated by a short synthesis of gamma-butyrolactone 24, a key intermediate in the synthesis of prostaglandin PGF(20).
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| 50. |
- Restorp, Per, et al.
(författare)
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Regioselective and Divergent Opening of Vinyl Epoxides with Ethoxyacetylene
- 2004
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; :18, s. 2086-2087
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Tidskriftsartikel (refereegranskat)abstract
- A divergent protocol for nucleophilic opening of vinyl epoxides with ethoxyacetylide has been developed and demonstrated to give complete regioselectivity depending on reaction conditions.
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