Dihydromahuba lactone

A large group of y-lactones with a similar structural relationship to litsenolides were found in the trunk wood of Clinostemon mahuba (70, 71). Those are seven dihydromahuba lactones of series A (9-15) (Tkble 6.2.2), seven dihydroma-huba lactones of series B (16-22) (Thble 6.2.3), and eight mahuba lactones (23-30) (Ihble 6.2.4). 

The relationship of the )9,y-substituents in dihydromahuba lactones of series A was determined to be threo and that in the series B as erythro by the LIS NMR techniques (71). Mahuba lactones carry an exomethylene group at C-5 of the butanolide ring. The long alkyl side chains in these lactones are in the same alkane-alkene-alkyne-type relationship as in litsenolides. Isodihydromahubano-lide 23-A (15) and -B (22), mahubanolide-23 (29), and isomahubanolide-23 (30) are larger than the rest by two carbon units. 

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