Highly diastereoselective, nucleophilic alkenoylation of enantiopure α-oxy- and α-amino-alkanals by lithiated [1-(p-toluenesulfonyl)alk-2-enyl] carbamates. Revision of the stereochemistry and application to the synthesis of a dihydroxyethylene dipeptide isostere

Article abstract of DOI:10.1055/s-1997-1156

The addition of lithiated [1-(p-toluenesulfonyl)alk-2-enyl] carbamates to α-stereogenic aldehydes proceeds with steric approach control according to the Felkin-Anh model to produce α'-carbamoyloxy-α,β-enones by carbonyl migration and elimination of p-toluenesulfinate. Conversion of two enones to 1,3-dioxan-2-one 9 and to (2S,3S,4S,5S)-methyl-5-(dibenzylamino)-4-(N,N-diisopropylcarbamoyloxy) -3-hydroxy-2-isopropyl-7-methyloctanoate (16a), respectively, furnished samples suitable for X-ray crystal structure analyses to confirm the stereochemical course of the addition step.