| Abstract
| - Chiral α- and β-hydroxy acids such as (S)-lactic acid, (S)-phenyllactic acid, (S)-mandelic acid, or(3R)-3-hydroxybutyric acid have been used as tether groups for intramolecular and diastereoselective[2 + 2] photocycloaddition of 3-oxocyclohexene carboxylic acid derivatives. Total regiocontrol towardthe straight adduct and high diastereoselectivities (up to 94%) were observed in the case of butenyllactate 11. After separation of the two diastereoisomers, cleavage of the chiral tether under basicconditions afforded cyclobutane lactones in good yield and enantiomeric pure form. An X-raystructure has been recorded that confirmed the relative and absolute configuration of the threecontiguous stereogenic centers assigned according to CD spectra.
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