SYNTHESIS OF ASPIROCHLORINE PRECURSORS

Synthesis of key precursors of aspirochlorine (1) and related compound s has been achieved in 5 steps from 1,4-diacetyl-2,5-piperazinedione ( 2), MCPBA mediated oxidative cyclization of 2-acetyl-3-salicylidene-2, 5-piperazinedione (4) yielded a spiro 3 H-benzofuranol derivative (6) stereoselectively. Bromination of 6 by a 2-fluoropyridinium salt and s odium bromide, followed by NBS treatment yielded dibromide mixtures (8 ). Conversion of produced dibromides (8) to dithioacetates (9) by pota ssium thioacetate afforded all of four possible diastereomers. The rat io of the diastereomers was found to be solvent dependent.