Synthesis of a thiashikimic acid derivative

Abstract

6-Thiashikimic acid has been synthesised as its racemic ethyl ester acetate 10. Ethyl thioxoacetato 3, generated thermally from the anthracene cycloadduct 2, reacted with 1,4-diacetoxybuta-1,3-diene 4 to give a pair of epimeric, Diels–Alder adducts 5 and 6. Each was converted with osmium tetroxide into the corresponding diol 7 and 8. The diol 7 underwent trans elimination of acetic acid in hot pyridine to give the 6-thiashikimic acid derivative 10. The configurations of both diols 7 and 8 were confirmed by X-ray crystal structure analysis. The conformations of the diols in the crystals and in solution are discussed in the light of their ¹H NMR spectra.