STRUCTURE AND SI-29 NMR-SPECTROSCOPY OF CHIRAL TRI-ALKOXYSILANES AND TETRA-ALKOXYSILANES - OBSERVATION OF RESTRICTED ROTATION OF 1,2 4,5-DI-O-ISOPROPYLIDENE-BETA-D-FRUCTOPYRANOSE/

A number of hindered, chiral alkyltrialkoxysilanes, tetraalkoxysilanes and chlorotrialkoxysilanes have been prepared, and studied. The X-ray structures of i-O-isopropylidene-beta-D-fructopyranos-3-O-yloxy) isob utyl(2-phenylethoxy)silane (1), di(1,2: ta-D-fructopyranos-3-O-yloxy)- (hexa-2,4-dienyloxy) vinylsilane (3) and (2-phenylethoxy)tri(1,2 i-O-i sopropylidene-beta-D-fructopyranos-3-O-yloxy) silane (6) are reported. In all structures the 1,2:4,5-diisopropylidene-beta-D-fructopyranose, one of the alkoxy-substituents, was found to have a fixed conformatio n about the O3-C3 bond with hydrogen and silicon being eclipsed.