Lanostane-to-cucurbitane transformation

Edwards, O. E.; Paryzek, Z.

doi:10.1139/v83-341

Cited by 12 publications

(1 citation statement)

References 14 publications

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“…The cucurbitacins are biogenetically derived from 2,3oxidosqualene via 10-cucurbita-5,24-dien-3-ol (cucurbitadienol) as the crucial intermediate (Shibuya et al, 2004). In chemical synthesis, the cucurbitane derivatives are available from the reaction of 9-substituted lanostane derivatives via C-9 carbocationic intermediates (Paryzek, 1976(Paryzek, , 1979Edwards & Paryzek, 1983;Edwards & Kolt, 1987).…”

Section: Commentmentioning

confidence: 99%

Two isomeric cucurbitane derivatives

2009

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Two isomeric cucurbitane derivatives, 3beta,7alpha,11beta-triacetoxycucurbit-5(10)-ene, (I), and 3beta,7alpha,11beta-triacetoxy-5alpha-cucurbit-1(10)-ene, (II), both C(36)H(58)O(6), have their single endocyclic C=C double bonds in different positions. This results in differences in the conformation of the four-ring system, which is close to a half-chair/half-chair/chair/half-chair arrangement in (I) and to a half-chair/twist-boat/boat/half-chair arrangement in (II). The orientation of some of the substituents is also different; the 3beta-acetoxy group is in an equatorial position in (I) but in an axial position in (II), while the 11beta-acetoxy group occupies an axial position in (I) and an equatorial position in (II). The asymmetric unit of (I) contains two symmetry-independent molecules which do not differ significantly, being related by a pseudo-twofold axis of symmetry. In both structures, the aliphatic chain fragments are disordered and the disorder persists at lower temperatures.

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