Comparison of solid-phase and solution-phase chiral auxiliaries in the alkylation/iodolactonization sequence to gamma-butyrolactones.

Five prolinol-based chiral auxilaries have been compared for the stereoselective synthesis of gamma-butyrolactones via the sequence of N-acylation, C(alpha)()-allylation, and iodolactonization under both solution-phase and solid-phase conditions. Comparisons of stereoselectivity of both the C(alpha)()-allylation and iodolactonization processes indicate that incorporation of a non-C(2)-symmetric auxiliary as a polymer cross-link gives results superior to those obtained either in solution or with other non-C(2)-symmetric auxiliaries and comparable to those observed using a polymer-supported pseudo-C(2)-symmetric auxiliary.