5- Thio-D-glucose

A Michael addition-Nef reaction sequence was used in a synthesis of disaccharides. Addition of the sodium salt of 1-thio-D-glucose to sugar nitroolefin 112 gave a mixture of isomers 113. The subsequent deacetylation, followed by a Nef reaction, afforded the S -disaccharides 114 and 115 (Scheme 35).82... 

A new method of stereoselective synthesis of thiodisaccharides by conjugate addition of 1-thio- D-glucose (8a) or 1-thio-a-L-fucose (30b) to an imsatura-ted carbohydrate molecule was also used for the preparation of o-glucopyrano-syl- and of L-fiicopyranosyl-thiodisaccharides [56]. 

D. Horton, 1-Thio-D-glucose, Methods Carbohydr. Chem., 2 (1963) 433-437 and references therein. 

The 1-thio-D-glucose derivative (15) has been synthesised from the corresponding free sugar (12) by treatment with 5,5 -bis( 1-phenyl-l f-tetrazoI-5-yl)dithiocarbonate, As indicated in Scheme 3, a thiocarbonate derivative (14) was formed initially with concomitant liberation of thiol (13). Direct attack by this thiol at C-1 (path a) gave the main product (15) in 63% yield, whereas benzyloxy participation in the displacement at C-1 with attack by the nucleophile at C-6 (path b) gave its regio-isomer (16) which was isolated in 33% yield. The use of compound (15) in silver triflate promoted glycosylations is referred to in Chapter 3. 

Section) imposes greater stereoelectronic control which leads to greater axial selectivity. Two reports have appeared on the preparation of etoposide (130) which is a clinical anticancer substance. Both use 1-thio-D-glucose compounds, but the first employs a bromine atom and the second a coordinated hydroxy group for leaving purposes. A 45% 3deld is claimed in the latter in the former report sulfoxide and sulfone analogues were described. 

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