Stepwise photochemical-chiral delivery in gamma-cyclodextrin-directed enantioselective photocyclodimerization of methyl 3-methoxyl-2-naphthoate in aqueous solution.

ABSTRACT

Irradiation of methyl 3-methoxyl-2-naphthoate (2,3-NA) with lambda > 280 nm results in photocyclodimerization to produce cubane-like photocyclodimer 1 and the [4 + 4] intermediate 2. The optically pure enantiomers of the intermediate 2 have been achieved by high-performance liquid chromatography (HPLC) resolution on a chiralcel OJ-RH column. Comparison of the enantiomeric excess (ee) values for photocyclodimer 1 and the intermediate 2 obtained in gamma-CD aqueous solution reveals the stepwise photochemical-chiral delivery for the first time, which is recognized to be a consequence of an in situ increase in the ee value from 39% for the [4 + 4] intermediate 2 to 48% for photocyclodimer 1 upon irradiation of 2,3-NA in the presence of gamma-CD.