CONTROLLING PI-FACIAL DIASTEREOSELECTIVITY IN THE 1,3-DIPOLAR CYCLOADDITIONS OF DIAZOMETHANE TO CHIRAL PENTENOATES AND FURANONES - ENANTIOSELECTIVE STEREODIVERGENT SYNTHESES OF CYCLOPROPANE HYDROXY-ACIDS AND DIDEHYDRO AMINO-ACIDS

The title compounds have been synthesized in both enantiomeric forms a nd in good overall yields by using D-glyceraldehyde as the single chir al precursor. The efficiency and usefulness of the synthetic routes ha ve been secured by performing controlled manipulations of the function al groups and by highly stereoselective transformations, namely Wittig -Horner condensations and cyclopropanations. Cyclopropane derivatives have been synthesized through 1,3-dipolar cycloaddition of diazomethan e to chiral pentenoates or furanones obtained, in turn, from D-glycera ldehyde. Syn/anti stereochemistry of the cycloadducts has been unequiv ocally assigned and rationalized. Since pi-facial diastereoselectivity involved in these cycloadditions is the opposite for cyclic and open- chain structures, enantiomeric series of products can be derived.