Highly stereocontrolled total synthesis of the polyether antibiotic salinomicin. II. Synthesis of right (C18-C30) segments from D-glucose, D-mannitol, and ethyl L-lactate.
Stereoselective synthesis of allylic amines by rearrangement of allylic trifluoroacetimidates: stereoselective synthesis of polyoxamic acid and derivatives of other α-amino acids
作者:Ian Savage、Eric J. Thomas、Peter D. Wilson
DOI:10.1039/a905772b
日期:——
On heating in xylene under reflux, allylic trifluoroacetimidates undergo [3,3] sigmatropic rearrangement to regioisomeric allylic trifluoroacetamides. Examples include the rearrangements of the trifluoroacetimidates 16 and 73 to the trifluoroacetamides 17 and 74, which were incorporated into stereoselective syntheses of polyoxamic acid 1, and the rearrangement of the trifluoroacetimidate 26. The rearrangement was the key step in asymmetric syntheses of the (S)- and (R)-valine derivatives 37 and 48. Other examples include rearrangements of the trifluoroacetimidates 52, 54 and 56 prepared from geraniol, cinnamyl alcohol and sorbyl alcohol, respectively, and the more complex trifluoroacetimidates 62 and 69. The stereoselectivity of these rearrangements, which are somewhat faster than rearrangements of analogous allylic trichloroacetimidates, is consistent with the participation of chair-like, six-membered, transition structures.
Iterative Synthesis of Deoxypropionate Units: The Inductor Effect in Acyclic Conformation Design
作者:Stephen Hanessian、Navjot Chahal、Simon Giroux
DOI:10.1021/jo061098o
日期:2006.9.1
Conjugateaddition of lithium dimethylcuprate to acyclic α,β-unsaturated esters of varying lengths bearing terminal alkyl or phenyl groups leads to a preponderance of syn 1,3-adducts when one methyl is already present. Conversion to enoates, and iteration of cuprateadditions also favors syn adducts to give contiguous deoxypropionate units in a growing chain. The effect of end-group variation (Me,
The dioxanone-to-dihydropyran Claisen rearrangement. Synthesis of C(7)-C(13) fragments of erythronolides A and B
作者:Steven D. Burke、Frank J. Schoenen、Mangalam S. Nair
DOI:10.1016/s0040-4039(00)95561-8
日期:——
Iterative applications of the dioxanone-to-dihydropyran Claisenrearrangement have resulted in the efficient conversion of (S)-(−)-ethyl lactate to the erythronolide A and B C(7)C(13) subunits 19, 23, and 27 via the common synthetic intermediates 13 and 22.
The Reformatsky-type condensation between methyl and t-butyl 3-(N,N-dimethylamino)propionates (9) and (10) with α-alkoxyaldehydes, which has been studied on varying the protective group of the aldehyde, proceeds with good diastereoselectivity.
The ester enolate claisen rearrangement. Synthesis of A C(1)C(6) erythronolide fragment
作者:Steven D. Burke、Frank J. Schoenen、Charles W. Murtiashaw
DOI:10.1016/s0040-4039(00)85502-1
日期:1986.1
An enantioselective route to the C(1)C(6) erythronolide unit 10 is described, involving the dioxanone-to-dihydropyran enolate Claisen rearrangement (7 → 8), regio- and stereoselective hydroboration to give 9a, and reductive fragmentation of the heterocyclic template (9c → 10).