Galactose dibenzyl dithioacetal

Dibenzyl dithioacetal, 4,5-O-isopropyli-dene See Galactose dibenzyl dithioacetal, G-194... 

Galactose dibenzyl dithioacetal - Galactose diethyl dithioacetal... 

Isopropylidene 4,5-0-Isopropylidene-D-galactose dibenzyl dithioacetal C23H30O5S2 450.619 Needles (EtOH). Mp 102.5-103°. [a]g +31 (CHCI3). 

O-Galactopyranosylglycerol a.-T>-(2Syform, G-150 Galactose dibenzyl dithioacetal D-form, G-194 Galactose diethyl dithioacetal D-form, G-195 Galactose 3-diltydrogen phosphate a-D-Pyranose-/orm ... 

Dithioacetal derivatives have also been employed56 in reactions with 23. The primary hydroxyl group in 2,3 4,5-di-0-isopropylidene-D-galactose diethyl and dibenzyl dithioacetals is readily replaced by iodine, to give the expected 6-deoxy-6-iodo derivatives in almost quantitative yields. The secondary hydroxyl group in 5-0-benzoyl-2,3-0-isopropylidene-L-arabinose diethyl dithioacetal (32) was similarly replaced by iodine to give 5-0-benzoyl-4-deoxy-4-iodo-2,3-O-isopropylidene-D-xylose diethyl dithioacetal (33) however, a rearranged product, namely, 4-0-benzoyl-5-deoxy-5-iodo-2,3-0-iso-propylidene-L-arabinose diethyl dithioacetal (34) was also produced. 

At reflux, the action of 3 equivalents of mercury(II) chloride in methanol converts the diethyl dithioacetal of D-glucose into a 5 1 mixture of methyl /3- and a-D-glucopyranoside299 extension of this reaction to the dibenzyl dithioacetal s of L-arabinose, L-rhamnose, and D-galactose afforded, as major products, the methyl /3-l-pyranoside of the L-pentose and the methyl a-pyranosides of the two hexoses, respectively.300... 

Glycosylation of 1,2 3,4-di-O-isopropylidene-D-galactose (412) with tri-0-acct l-5-thio-L-arabinopyranosyl bromide (411) in the presence of silver triflate and tetramethylurea gave the 5-lhiodisacharide 413, Compound 411 was obtained from acetylated 5-G-losyl-L-arabinose dibenzyl dithioacetal by cyclization with sodium iodide-barium carbonate in butanone (82%) followed by bromination with Br in CCI4 (76%).2 2... 

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