CYCLIZATION OF 3-AMINOACRYLATES - TOTAL SYNTHESIS OF PUMILIOTOXIN-C AND RELATED STEREOISOMERIC COMPOUNDS

A method is described for the synthesis of pumiliotoxin C (1a) and rel ated stereoisomeric compounds Ic-lf. Starting from (+)- or (-)-3-methy lcyclohexanone (6a,b), the oxo esters 7a and 7b were prepared. Condens ation with (+)- or (-)-3-ambnohexanol (8a,b) gave the stereoisomeric 3 -aminoacrylates Sa, Sb and Sc. The hydroxy group of the aminoacrylates was transformed into bromide using the tosylate method. Cyclization o f the bromides led to unsaturated quinoline ring systems. Finally, dec arboxylation and catalytic hydrogenation gave the different cis- and t rans-fused stereoisomeric alkaloids of the pumiliotoxin C type. The st ructures were verified by X-ray analysis.