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- Title
Synthèse de spiro-pyrazolines par cycloaddition du diazométhane sur des sucres insaturés ramifiés. Influence de l'isomérie géométrique sur l'orientation de la réaction Communication préliminaire
- Authors
Tronchet, Jean M. J.; Gentile, Bernard; Tronchet, Jeannine
- Abstract
The orientation of the cycloaddition of diazomethane on unsaturated branchedchain sugars has been studied. For 3- C-cyanomethylidene-3-deoxy-1,2- O-isopropylidene-α-D- glycero-tetrofuranose the orientation was 'normal' and did not depend on the configuration at the double bond. The same situation prevailed with derivatives of 3-deoxy-1,2:5,6-di- O-isopropylidene-3- C-methylidene-α-D-xylo-hexofuranose. For the 3- C-acylmethylidene- and the 3- C-cyanomethylidene-3-deoxy-1,2:5,6-di- O-isopropylidene-α-D- ribo-hexofuranoses, the trans-(H-C(3′)-C(2))-isomer gave the 'normal' cycloadduct whereas the cis-isomer gave predominantly the αabnormal spiro-pyrazoline. This observation represents the first instance where the regioselectivity of a cycloaddition reaction is affected by the geometrical isomerism of the dipolarophile. The most probable explanation of the phenomenon is the conformational perturbation about the C(4)--C(5) bond of the unsaturated sugars induced by a change in the configuration at C(3). The consequence of that 'conformational transmission' of a difference in configuration at C(3) is that the steric crowding on the cis- than in the trans-isomer. Several novel examples of a new series of C-glycosylidenic derivatives, the spiro-pyrazolines, are described.
- Publication
Helvetica Chimica Acta, 1975, Vol 58, Issue 6, p1817
- ISSN
0018-019X
- Publication type
Article
- DOI
10.1002/hlca.19750580637