Addition of Organolithium Reagents to Some Carbohydrate Enones
作者:Osman Achmatowicz、Barbara Szechner、Jan K. Maurin
DOI:10.1016/s0040-4020(97)00253-6
日期:1997.4
Addition of organolithiumreagents to the sugar enones: alkyl 2,3,6-trideoxy-α-l- and 2,3-dideoxy-α-d-hex-2-enopyranosid-4-ulose has been examined. Butyl, benzyl and 2,5-dimethoxy-4-methylphenyllithium add, with increasing stereoselectivity, to the carbonyl group of the α,β-unsaturated ketosugars, whereas 2,5-dimethoxybenzyllithium undergoes stereospecific conjugate addition and 1,2-addition in the
Palladium-catalyzed trimethylenemethane reaction to form methylenetetrahydrofurans. Aldehyde and ketone substrates and the tin effect
作者:Barry M. Trost、Steven A. King、Thomas Schmidt
DOI:10.1021/ja00197a060
日期:1989.7
Le meilleur cocatalyseur est l'(acetoxy trimethyl) stannane. L'acetate de trimethylsilylmethyl-2 allyle est utilise comme precurseur du trimethylenemethane
Le meilleur cocatalyseur est l'(乙酰氧基三甲基)锡烷。L'acetate de trimethylsilylmethyl-2 allyle est利用三亚甲基甲烷的前体
Heterocyclic Acceptors in Diastereoselective Palladium Mediated [3+2] Cycloadditions
作者:Barry M. Trost、Steven A. King、Thomas N. Nanninga
DOI:10.1246/cl.1987.15
日期:1987.1.5
Whereas cyclohexenones and ketones are poor acceptors for palladium mediated cycloadditions of 2-trimethylsilylmethylallylacetate, oxygen heterocycles bearing such functionality react smoothly and with high diastereoselectivity.
Catalytic tin radical mediated tricyclisations. Part 1. Monocyclisation studies †
作者:David R. Kelly、Mark R. Picton
DOI:10.1039/b000661k
日期:——
A general strategy for catalytic tin radical mediated, radical cascade reactions is proposed in which three rings are constructed in a single step. The initial step in the tricyclisation process has been examined using 2,3-dideoxy-α-D-erythro-hex-2-enopyranosides bearing unsaturated substituents at the 1-O and/or 4-O-positions. Substrates for cyclisation of substituents at the 1-O-position were prepared by a novel zinc chloride catalysed Ferrier rearrangement of tri-O-acetyl-D-glucal with unsaturated alcohols, whereas substrates for cyclisation of substituents at the 4-O-position were prepared by alkylation or acylation of ethyl 6-O-protected 2,3-dideoxy-α-D-erythro-hex-2-enopyranosides. Propargyl substituents cyclise efficiently, but propenyl substituents less so. Propioloyl substituents undergo hydrostannylation without cyclisation.
Photochemical access to alkyl 3-deoxyglycopyranosid-4-uloses
作者:Janine Cossy、Said Ibhi
DOI:10.1016/0008-6215(94)84205-1
日期:1994.6
lipopolysaccharides, conferring on them their serological specificity [2]. A general synthetic approach to these sugars involves the stereoselective reduction of aldose derived epoxides [3]. Alternatively they have been prepared from furfuryl aIcohols [4] by deamination of methyl 3-amino-3-deoxy-P-o-allopyranoside [5] or from methyl 4,6-0-benzylidene-3-deoxy-~-o-ti~o-hexopyranoside [6] in modest yields. In connection