Enantioselective synthesis of 1-nitrotricyclo[5,2,2,02,6]undeca-3,8-dienes via tandem consecutive asymmetric Diels–Alder reaction–Cope rearrangement
摘要:
The 1-glyco-2-nitrocyclohexa-2,4-dienes 1a and 5a react with cyclopentadiene to yield, almost exclusively, the 10-glyco-1-nitrotricyclo[5,2,2,0(2,6)]undeca-3,8-dienes 4a and 8a. Formation of these products is explained as the result of a tandem consecutive asymmetric Diels-Alder reaction-Cope rearrangement. Periodate oxidation of deprotected sugar side-chains, followed by sodium borohydride reduction yielded enantiomerically pure 10-formyl- and 10-hydroxymethyl-1-nitrotricyclo[5,2,2,0(2,6)]undeca-3,8-dienes. Structures have been determined by X-ray crystallographic and spectroscopic analyses, and chemical correlation. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.
Studies on the reactivity of (pentitol-1-yl)nitrocyclohexadienes with acetyl chloride in methanol
作者:M. Baños、E. Román、J.A. Serrano
DOI:10.1016/s0957-4166(03)00155-1
日期:2003.5
(Pentitol-1-yl)nitrocyclohexadienes with pentaacetylated D-galacto and D-manno sugar side-chains react in different ways when they are subjected to transesterification with acetyl chloride in methanol. Although both processes should commence with a deacetylation, subsequent intramolecular nucleophilic attack from the resulting hydroxyl groups on electrophilic carbons on the cyclohexadiene ring was dependant on the nature of the sugar side-chain, as well as on the configuration at the stereogenic carbon of the cyclohexadiene ring. Thus, D-manno nitrocyclohexadiene led to a complex mixture from which we could either isolate or identify products with dioxatricyclodecane dimethyl ketal, benzofuran, chromane-3,4-diol, bicyclic or tricyclic oximes, nitrobenzene, and nitrocyclohexenol structures. In contrast, D-galacto nitrocyclohexadiene led exclusively to a bicyclic oxime. (C) 2003 Elsevier Science Ltd. All rights reserved.