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Madeiranes, a New Class of Pentacyclic Triterpenes: D ‐Friedo‐madeir‐14‐en‐3β‐ol and ‐3‐one, D : C ‐Friedomadeir‐7‐en‐3β‐ol and ‐3‐one
Author(s) -
Ferreira MariaJosé Umbelino,
Lobo Ana M.,
O'Mahoney Caroline A.,
Williams David J.,
Wyler Hugo
Publication year - 1991
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19910740622
Subject(s) - chemistry , cyclopentane , stereochemistry , ring (chemistry) , terpene , triterpene , hopanoids , tricyclic , organic chemistry , medicine , paleontology , alternative medicine , pathology , structural basin , source rock , biology
Abstract The pentacyclic triterpenes 1a, b and 2a, b are isolated from extracts of Euphorbia mellifera Arr. Their structures, determined by X‐ray analysis, are supported in part by MS, NMR, and IR data. The skeleton differs from that of representatives of the lupane or hopane class by ( i ) an unusual arrangement of the substituents in the cyclopentane ring E, the Me group being on C(19) and the i‐Pr group in an angular position on C(17), and ( ii ) a cis D/E ring junction. We propose to name Die unknown pentacyclic parent ‘madeirane’, thus 1a, b and 2a, b are D ‐friedomadeir‐14‐ene and D : C ‐friedomadeir‐7‐ene derivatives. The biosynthesis of these compounds may be rationalized via ‘spirodammaranol’‐cation intermediates 5 and 5′ and madeiranol cation 6 , as outlined in Scheme 2 .