C-6 ALLYLATED PYRANOSIDES FOR THE SYNTHESIS OF COMPLEX OXYGENATED TETRAHYDROFURANS

The iodoetherification of C6 allylated D-pyranosides containing an all ylic benzyloxy substituent, and their acyclic 5-hexen-, 1,2,4-triol an alogs were performed. Pyranosides of R configuration at the allylic et her gave exclusively a syn,syn-2,5-dialkyi-3-oxy-tetrahydrofuran which is primed for elaboration into several classes of naturally occurring THF's. By comparison, the stereoselectivity for the non-pyranoside de rivative was much lower. In the S series, the bias was opposite for th e pyranoside vs, the non-pyranoside substrates, but the selectivity in both cases was low. (C) 1997 Elsevier Science Ltd.