Oxazoline N-oxide-mediated [2+3] cycloadditions. Application to a synthesis of (-)-tetrahydrolipstatin.

[reaction: see text] A [2+3] cycloaddition of camphor-derived oxazoline N-oxide to alpha,beta-unsaturated ester afforded adduct 8. Tetrahydrolipstatin 1 was prepared from this compound in a nine-step sequence of reactions.