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Chemical Transformations of 6a-Acetoxyazadirone and Two-dimensional NMR Studies on Tetranortriterpenoids
A PATRA, T K MANDAL, A MAJUMDAR, K K MANDAL
Published in -
1998
Volume: 75
   
Issue: 43750
Pages: 804 - 809
Abstract
Basic hydrolysis of the tetranortriterpenoid 6α-acetoxyazadirone yielded 6α-hydroxydeacetylazadirone which on preferential acetylation in the cold afforded 6α-acetoxydeacetylazadirone. Treatment of 6α-acetoxyazadirone with hydrogen peroxide-selenium dioxide gave 6- O-acetylisonimocinolide which was a constituent of Chisocheton paniculatus and it underwent acetylation with acetic anhydride-pyridine to 6,21-di-O-acetylisonimocinolide. Careful hydrogenation of 6α-acetoxyazadirone gave 1,2-dihydro as well as 1,2,20,21,22,23- hexahydro derivatives which were hydrolysed under basic conditions to the corresponding 6,7-diol, 6α-Hydroxy-1,2- dihydrodeacetylazadirone so derived furnished meldenin, a minor phytoconstituent of Melia azadirachta, on preferential acetylation in the cold and a triol upon NaBH4 reduction. Acetylation of the latter afforded a triacetate. The structures and nmr assignments of the compounds were settled from two-dimensional homonuclear and heteronuclear correlation (optimized for one-bond and long-range C- H couplings) studies.
About the journal
JournalJournal of the Indian Chemical Society
Publisher-
ISSN0019-4522