Total Syntheses of Conformationally Locked Difluorinated Pentopyranose Analogues and a Pentopyranosyl Phosphate Mimetic
摘要:
Trifluoroethanol has been elaborated, via a telescoped sequence involving a metalated difluoroenol, a difluoroallylic alcohol, [2,3]-Wittig rearrangement, and ultimately an RCM reaction and requiring minimal intermediate purification, to a number of cyclooctenone intermediates. Epoxidation of these intermediates followed by transannular ring opening or dihydroxylation, then transannular hemiacetalization delivers novel bicyclic analogues of pentopyranoses, which were elaborated (in one case) to an analogue of a glycosyl phosphate.
Total Syntheses of Conformationally Locked Difluorinated Pentopyranose Analogues and a Pentopyranosyl Phosphate Mimetic
摘要:
Trifluoroethanol has been elaborated, via a telescoped sequence involving a metalated difluoroenol, a difluoroallylic alcohol, [2,3]-Wittig rearrangement, and ultimately an RCM reaction and requiring minimal intermediate purification, to a number of cyclooctenone intermediates. Epoxidation of these intermediates followed by transannular ring opening or dihydroxylation, then transannular hemiacetalization delivers novel bicyclic analogues of pentopyranoses, which were elaborated (in one case) to an analogue of a glycosyl phosphate.
Selected Substituent Effects on the Rate and Efficiency of Formation of an Eight-Membered Ring by RCM
作者:Lisa Mitchell、John A. Parkinson、Jonathan M. Percy、Kuldip Singh
DOI:10.1021/jo702726b
日期:2008.3.1
highlight a discrepancy between cyclization rate and cyclization efficiency. Cyclization rates change modestly as the oxygen function at the allylic position is varied, and increase upon gem-dimethylation. Cyclization efficiency has also been quantified for four substrates, revealing a range of effective molarities (EMs) of 2 orders of magnitude that are substituent dependent. The most efficient cyclization