Ehretia aspera

A new type of pyrrolizidine alkaloid has been isolated from the leaves of Ehretia aspera Willd. by Suri et al.n The structure (39) for ehretinine was established by spectroscopic evidence and by hydrolysis to give retronecanol and p-methoxy-benzoic acid. Confirmation of the structure (39) was obtained by synthesis of ehretinine from retronecanol and pmethoxybenzoyl chloride. This is the first reported occurrence of a retronecanol ester, although it should be pointed out that retronecanol esters can be produced by hydrogenolysis of retronecine diesters. The authors do not appear to have considered the possibility that ehretinine could have been formed by hydrogenolysis of the common type of ester (40) on treatment with the zinc and sulphuric acid that are used in their extraction procedure. 

Ehretia aspera Willd. Heliotropium amplexicaule Vahl. H. arbainense H. arborescens L. 

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