New Chiral Auxiliaries and New Optically Pure Ketene Equivalents Derived from Tartaric Acids. Improved Synthesis of (-)-7-Oxabicyclohept-5-en-2-one

Article abstract of DOI:10.1016/S0957-4166(00)82385-X

Condensation of di-O-acetyl (R,R)- and (S,S)-tartaric anhydride with acetals of N-alkylaminoacetaldehyde gave new chiral auxiliaries (1R,5S,7R)- and (1S,5R,7S)-3-alkyl-2-oxo-3-aza-6,8-dioxabicyclo<3.2.1>octane-7-carboxylic (RADO(alkyl)-X and SADO(alkyl)-X) derivatives, respectively.The latter could be used to generate the corresponding 1-cyanovinyl esters that add to furan to give readily crystallizable, optically pure Diels-Alder adducts.The method was illustrated by application to the synthesis of (-)-(1S,4S)-7-oxabicyclo<2.2.1>hept-5-en-2-one.