Dicinnamates photocycloaddition

The diastereoselection of the intramolecular photocycloaddition of 1,4-erythritol dicinnamates (161b) has been explained by diastereoisomeric transition states involving different steric constraints and on the basis of a simulation of the diastereomeric ground-state conformations believed to lead to the observed adducts. Modification of the chiral auxiliary in 161c led to disappointing selectivities and the chemical yields in the desired 5-truxinate remained low. 

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