Synthesis and Absolute Configuration Of（（2r,3r,6s）-3-hydroxy-6-（naphthalen-2-ylthio）-3,6-dihydro-2h-pyran-2-yl）methyl Pivalate

A stereo-selective palladium-catalyzed one-pot Tsuji-Trost reaction was used to prepare four fl-thiogalactosides from unsaturated D-galactal and thiol. Their structures were characterized by nuclear magnetic resonance spectra and high-resolution electrospray ionization mass spectra. The absolute configuration was confirmed with a Flack parameter of 0.019(15) by X-ray crystallography using a Cu radiation source. Compound 6a (C21H24O4S): orthorhombic system, space group P2(1)2(1)2(1), a = 9.0919(4), b = 9.6313(4), c = 22.5936(11) angstrom, V = 1978.45(15) angstrom(3), Z = 4, F(000) = 792, Dc = 1.250 g/cm(3), mu = 1.636 mm(-1), R = 0.0478 and wR = 0.1384 for 3621 independent reflections (R-int = 0.0390) and 3326 observed ones (I > 2 sigma(I)). 3-(4,5)-Dimethylthiazol-2-yl-2,5diphenyltetrazolium bromide (MTT) cell viability assays indicated that these thiogalactosides showed anti-proliferative activities against human gastric cancer HGC-27 cells with IC50 values of 69 similar to 88 mu M.