Mexicanolide derivatives

Although these are not yet known, 30a-acyloxy-8,14-oxides are. The 8,30-double bond is also resistant to oxidation in the laboratory, and compounds of this type have not been prepared synthetically. Structural elucidation of all these compounds follows readily from n.m.r. spectroscopy the use of n.m.r. is particularly useful in detecting the various oxygen functions. Only one mexicanolide derivative is so far known which is substituted in ring C this is an lip-acetate (49) isolated from Khaya senegalensis (13,151). 

Among related new compounds are 6-hydroxy carapin (110) from Cedrela glaziovii the 3jS-acetate (111) from K. nyasica, and the lactone (112) derived from mexicanolide, from K. ivorensis. Full papers have appeared on nyasin from K. nyasica, khayanthone from K. anthotheca,and 1 l)8-acetoxykhivorin from K. madagascariensis. ... 

Compounds of this group are derived from 1,3-diketodiene lactones of the andirobin group by spontaneous Michael cyclisation, producing mexicanolide in the simplest case (75, 76,144). In the synthesis (Scheme 9)... 

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