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Some Interesting Reactions of Gelomulides, the Natural Diterpene Lactones
S K TALAPATRA, P PAL, G DAS, K BISWAS, A POREL, B TALAPATRA
Published in INDIAN CHEMICAL SOC
1997
Volume: 74
   
Issue: 43781
Pages: 848 - 854
Abstract
Some interesting chemical reactions involving the characteristic features and confirming the proposed stereostructures of gelomulides A-F (1-6), the closely related diterpene lactones from the leaves of Gelonium multiflorum (Fam. Euphorbiaceae) and some chemical correlations were carried out. Thus, 3 upon treatment with the DDQ gave 4 which was also produced when 6 was treated with pyridine or methanolic NaHCO3. Zn dust/AcOH (reflux) or PPh3/I2 deepoxidized 1 and 4 to 13 and 14 respectively. PPh3/I2 converted 6 to the corresponding olefin 15 which upon refluxing with pyridine afforded 14, also obtained directly from 6 by refluxing with Zn dust/ AcOH. NaBH4 reduction of 3 and 6 gave the corresponding tetrahydro derivatives 18 and 21; additionally, 1 and 6 gave 19 and 20 respectively. Compound 1 underwent base-catalyzed opening of the lactone and the epoxide rings, followed by ring C aromatization to give 16. Similarly, under three different acidic conditions, 4 and 6 gave the same product 17. Catalytic hydrogeneration of different gelomulides caused the hydrogenolysis of the allylic epoxide bond and reduction of the Δ1,2 bond (if present) but the 3-CO group remained unaffected. The formation of the products have been rationalized in terms of the assigned stereostructures and molecular conformations of the gelomulides.
About the journal
JournalJournal of the Indian Chemical Society
PublisherINDIAN CHEMICAL SOC
ISSN0019-4522