ON THE STEREOCHEMICAL OUTCOME OF THE REACTION BETWEEN (-)-CHORISMIC ACID AND DIAZOMETHANE - ABSOLUTE PROOF OF STEREOCHEMISTRY OF THE MAJOR PYRAZOLINE BY X-RAY CRYSTALLOGRAPHY OF A CYCLOPROPANE BASED DERIVATIVE

Reinvestigation of the reaction between (-)-chorismic acid and diazome thane in diethyl ether on a larger scale has shown that the previously reported single pyrazoline based product is accompanied by a stereois omer that results from the addition of diazomethane to the more hinder ed alpha-face of the chorismate 1,2-double bond (alpha :beta addition ca. 1:6). Thermolysis of the two cycloadducts at 80 degrees C afforded a pair of cyclopropane derivatives with stereochemistry that could no t be confidently assigned using data from coupling constants alone. NO E data allowed a more confident assignment of the stereochemistry of t he two cyclopropanes; the beta-cyclopropyl derivative was saponified a nd hydrolysed to yield a bicyclo[4.1.0]hept-2-ene-1-carboxylic acid de rivative that was unequivocally shown to possess(1S,4R,5R,6R)-stereoch emistry by an X-ray crystallographic study.