Structural and ¹H and ¹³C NMR analysis of two new glabretal triterpenoid derivatives from Guarea jamaicensis

Abstract

The 1 H and 13 C NMR spectra of the glabretal derivatives, 21,24-epoxy-3a, 7a, 21,23-tetraacetoxy-25-hydroxy4a,4b,8b-trimethyl-14,18-cyclo-5a, 13a, 14a, 17a-cholestane and 21,23-epoxy-3a, 7a,21,24,25-pentaacetoxy4a, 4b, 8b-trimethyl-14,18-cyclo-5a, 13a, 14a, 17a-cholestane, obtained from an acetylated fraction of extracts of Guarea jamaicensis, were completely assigned. 1D NMR and a number of 2D shift correlated NMR exper-

Terpenoid constituents from leaves of Guarea kunthiana

“…21 This compound, which has been obtained from leaves of several angiosperms, was also isolated from Guarea jamaicensis. 22 Although members of the Meliaceae, including those belonging to the genus Guarea that occur in Brazil, are well-known for the occurrence of sesqui-, di-, tri-and tetranortriterpenoids, 1,13,23 the isolation for the first time of cembranoid and kaurenoid diterpenes in this family is noteworthy for its chemosystematic relevance. Also worthy of mention is the fact that, unlike the specimen of G. kunthiana found in Ecuador whose aerial parts yielded one limonoid as the only natural compound, no limonoids were detected in the leaves of the specimen collected in Brazil and investigated in the present work.…”

Triterpenoids

“…Eight new tirucallanes, dyvariabilins A-H 130-137, have been reported from Dysoxylum variabile 74 while another, 138, was found in Dysoxylum malabaricum. 37 Other compounds in this series include the apotirucallane 139 from Azadirachta indica, 75 the 14,18-cycloapotirucallanes 140 and 141 from Guarea jamaicensis 76 and the nor-derivatives malabanones A 142 and B 143 from Ailanthus malabarica. 77…”