Synthesis of jenamidines A1/A2.

[reaction: see text] Addition of the enolate of tert-butyl acetate to cyanamide methyl ester 17 followed by treatment with LHMDS afforded vinylogous urea 19 in 27% yield. Vinylogous urea 19 was also obtained from 37 and tert-butyl cyanoacetate in 50% yield. Acylation of 19 with acid chloride 31d, followed by hydrolysis of the tert-butyl ester and decarboxylation with 9:1 CH2Cl2/TFA and very mild basic hydrolysis of the methoxyacetate ester, afforded jenamidines A1/A2 (3) in 45% yield. This first synthesis confirms our reassignment of the jenamidines A1/A2 structure.