Probing the stereoselectivity of the Heck arylation of endocyclic enecarbarnates with diazonium salts.: Concise syntheses of (2S,5R)-phenylproline methyl ester and Schramm's C-azanucleoside

[GRAPHICS] The diastereoselectivity of the Heck arylation of several chiral, nonracemic, five-membered endocyclic enecarbamates with aryldiazonium tetrafluoroborates was evaluated. The cis selectivity observed for some enecarbamates bearing coordinating groups was explored in the concise synthesis of the (2S,5R)-(+)-phenylproline methyl ester, a scaffold for the nonpeptide cholecystokinin antagonist (+)-RP 66803, and in the synthesis of Schramm's potent antiprotozoan C-azanucleoside.