Studies toward the synthesis of pinolidoxin, a phytotoxic nonenolide from the fungus Ascochyta pinodes. Determination of the configuration at the C-7, C-8, and C-9 chiral centers and stereoselective synthesis of the C-6-C-18fragment

The absolute stereochemistry at the C-7, C-8, and C-9 chiral centers of pin olidoxin (1) has been determined by chemical and spectral methods. First, t he synthesis of four stereoisomeric fully benzoylated 2,3-erythro-1,2,3,4-h eptanetetrols, corresponding to the C-6-C-18 portion of the natural substan ce, has been accomplished starting from meso-tartaric acid. As next step, t he selection of the synthetic tetrabenzoate possessing "natural" stereochem istry (10a'), suitable for absolute configuration determination, has been c arried out by correlation with its "natural" homologue derived from degrada tion of pinolidoxin. Determination of the stereochemistry at the title chir al centers has been carried out by application of the Mosher's method both to 7a', a compound stereochemically related to 10a', and to pinolidoxin its elf. The stereoselective synthesis of a protected form of the C-6-C-18 port ion of pinolidoxin, to be used in its total synthesis, has also been accomp lished starting from commercially available D-erythronolactone.