TIN IN ORGANIC SYNTHESIS .9. OBSERVATIONS ON DIBUTYLSTANNYLENE AS TEMPLATE FOR THE ASSEMBLY OF MACROCYCLIC OLIGOLACTONES

Dibutylstannylene-mediated macrolactonization of methyl 4,6-O-benzylidene-alpha-D-glucopyranoside (2) with glutaryl and phthaloyl dichloride yields the respective dilactones 6e and 6f and parallel tetralactones Se and 5f as well as the antiparallel tetralactone 4e in the case of glutarylation. The reaction with malonyl dichloride yields a negligible amount of the parallel tetralactone 5d and that of fumaryl and isophthaloyl dichloride yields polyesters only, a byproduct in all these reactions. The mechanism of stannylene-mediated macrolactonization is discussed incorporating data pertaining to known hexa- and octalactone formation when succinyl dichloride is used. A correlation between stannylene dimer symmetry and tetralactone constitutional isomer selectivity is introduced.