ETA(6)-TRICARBONYLCHROMIUM COMPLEXES OF METHYL 4,6-O-BENZYLIDENE-ALPHA-D-GLUCO-PYRANOSIDES

The structures of the eta(6)-tricarbonylchromium complexes of four met hyl 4,6-O-benzylidene-alpha-glucopyranosides, (2)-(5), have been deter mined, as well as that of the free monosaccharide, (1). These compound s are (R)-methyl O-methyl-4,6-O-benzylidene-alpha-D-glucopyranoside [( 1), C16H22O6], tricarbonyl{(R)-methyl -benzylidene)-alpha-D-glucopyran oside}-chromium(0) {(2), [Cr(C16H22O6)(CO)(3)]}, tricarbonyl-{(R)-meth yl enylmethylene]-alpha-D-glucopyranoside}chromium(0) {(3), [Cr(C17H24 O6S)(CO)(3)]}, tricarbonyl{(R)-methyl enylmethylene]-alpha-D-glucopyra noside}chromium(0) dichloromethane solvate {(4), [Cr(C28H31O6P)(CO)(3) ].-CH2Cl2} and tricarbonyl[(R)-methyl enylmethylene)-alpha-D-glucopyra noside]chromium(0) {(5), [Cr(C17H24O7)(CO)(3)]}. These structural stud ies were undertaken to establish the solid-state conformation of the c omplexed arene ring in the 4,6-O-benzylidene and the 4,6-O-p-methoxyph enylmethylene eta(6)-Cr(CO)(3) complexes, and also the absolute stereo chemistry of some ortho-substituted derivatives of the 4,6-O-benzylide ne complex.