Convenient one-pot synthesis of thiosugars and their efficient conversion to polyoxygenated cycloalkenes

A convenient synthesis of polyoxygenated tetrahydrothiopyrans and thiepanes from various alditol derivatives with xylo, ribo, manno, gluco, galacto, and fuco configurations is described. The preparation started from the corresponding partially protected alditols and proceeded in a 'one-pot' manner to afford the final products in 80%-95% yield. Furthermore, thiosugar compounds 2b, 2d, and 2g were converted to the optically pure polyoxygenated cycloalkenes through Ramberg-Backlund reaction in moderate to good overall yield. The procedures can be used for the preparation of polyoxygenated thiosugars and cycloalkenes on a relatively large scale.