Synthesis of 2-iodo-2-deoxy septanosides from a D-xylose-based oxepine: intramolecular cyclization in the absence of a glycosyl acceptor.

Oxidative glycosylations of the D-xylose-based oxepine 1,6-anhydro-3,4,5-tri-O-benzyl-2-deoxy-D-xylosept-1-enitol (1) using N-iodosuccinimide (NIS) are reported. The reaction produced 2-deoxy-2-iodo-alpha-D-idoseptanosides and 2-deoxy-2-iodo-beta-D-guloseptanosides 2-9 in good yields. When limited equivalents of a glycosyl acceptor were used, or in the absence of a glycosyl acceptor, an intramolecular cyclization predominated to form 1,6-anhydro-3,4-di-O-benzyl-2-deoxy-2-iodo-alpha-D-idopyranose (10).