Hetero [6+3] cycloaddition of fulvenes with N-alkylidene glycine esters: a facile synthesis of the delavayine and incarvillateine framework.

[reaction: see text] In contrast to the [3+2] or [4+3] cycloaddition of N-metalated azomethine ylides and various alkenes, N-benzylidene glycine ethyl ester reacts with fulvenes to give the hetero [6+3] cycloaddition adducts with high stereoselectivity, constituting an efficient and novel route to [2]pyrindines.