| 1. |
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Perez-Escobar, O. A., et al.
(författare)
-
Molecular Clocks and Archeogenomics of a Late Period Egyptian Date Palm Leaf Reveal Introgression from Wild Relatives and Add Timestamps on the Domestication
- 2021
-
Ingår i: Molecular Biology and Evolution. - : Oxford University Press (OUP). - 0737-4038 .- 1537-1719. ; 38:10, s. 4475-4492
-
Tidskriftsartikel (refereegranskat)abstract
- The date palm, Phoenix dactylifera, has been a cornerstone of Middle Eastern and North African agriculture for millennia. It was first domesticated in the Persian Gulf, and its evolution appears to have been influenced by gene flow from two wild relatives, P. theophrasti, currently restricted to Crete and Turkey, and P. sylvestris, widespread from Bangladesh to the West Himalayas. Genomes of ancient date palm seeds show that gene flow from P. theophrasti to P. dactylifera may have occurred by similar to 2,200years ago, but traces of P. sylvestris could not be detected. We here integrate archeogenomics of a similar to 2,100-year-old P. dactylifera leaf from Saqqara (Egypt), molecular-clock dating, and coalescence approaches with population genomic tests, to probe the hybridization between the date palm and its two closest relatives and provide minimum and maximum timestamps for its reticulated evolution. The Saqqara date palm shares a close genetic affinity with North African date palm populations, and we find clear genomic admixture from both P. theophrasti, and P. sylvestris, indicating that both had contributed to the date palm genome by 2,100years ago. Molecular-clocks placed the divergence of P. theophrasti from P. dactylifera/P. sylvestris and that of P. dactylifera from P. sylvestris in the Upper Miocene, but strongly supported, conflicting topologies point to older gene flow between P. theophrasti and P. dactylifera, and P. sylvestris and P. dactylifera. Our work highlights the ancient hybrid origin of the date palms, and prompts the investigation of the functional significance of genetic material introgressed from both close relatives, which in turn could prove useful for modern date palm breeding.
|
|
| 5. |
|
|
| 6. |
- Dayaker, G., et al.
(författare)
-
Enantioselective deprotometalation of alkyl ferrocenecarboxylates using bimetallic bases
- 2021
-
Ingår i: New Journal of Chemistry. - : Royal Society of Chemistry (RSC). - 1144-0546 .- 1369-9261. ; 45:48, s. 22579-22590
-
Tidskriftsartikel (refereegranskat)abstract
- The enantioselective deprotometalation of alkyl ferrocenecarboxylates (FcCO(2)R) using mixed lithium-zinc or lithium-cadmium bases is described. By using FcCO(2)Me as the substrate, chiral lithium alkyl-amidozincates prepared from exo-(alpha R)- or endo-(alpha S)-N-(alpha-phenylethyl)bornylamine (H-exo-born-R or H-endo-born-S) were tested; the best results (27% yield and 62% ee in favor of the R-P enantiomer) were obtained by using Bu-2(endo-born-S)ZnLi in tetrahydrofuran (THF) at -30 degrees C before iodolysis. Due to the low compatibility of FcCO(2)Me with alkyl-containing lithium zincates, 1 : 1 mixtures of lithium and zinc amides were tested. Chiral (H-exo-born-R or H-endo-born-S) or/and achiral (lithium 2,2,6,6-tetramethylpiperidide or lithium diisopropylamide) secondary amines gave good results, the best (81% yield and 44% ee in favor of the R-P enantiomer) being obtained by using (endo-born-S)(3)ZnLi in THF at room temperature. Among other secondary amines also prepared and/or tested, commercial (S,S)-bis(alpha-phenylethyl)amine (H-PEA-S) proved promising. After optimization of the reaction conditions, the best enantioselectivity (26% yield and 80% ee in favor of the RP enantiomer) was observed by treating a THF solution of FcCO(2)Me and Zn(PEA-S)(2) with Li-PEA-S at -80 degrees C before iodolysis. That no reaction took place with cadmium instead of zinc suggests the formation of 'ate complexes upon treatment of Cd(PEA-S)(2) by Li-PEA-S while Zn(PEA-S)(2) and Li-PEA-S would rather work in tandem (Li-PEA-S as the base and Zn(PEA-S)(2) as the in situ trap for the formed ferrocenyllithium). While FcCO(2)Me, FcCO(2)tBu and FcCO(2)iPr could be converted into their racemic 2-iodinated derivatives with a yield of 84 to 87% by employing LiTMP (2 equiv.) in the presence of ZnCl2.TMEDA (1 equiv.) as an in situ trap, their enantioselective deprotometalation rather required Li-PEA-S together with Zn(PEA-S)(2) to produce the enantio-enriched derivatives with yields of 45-82% and 71% ee.
|
|
