5- Thio-D-ribose

Thio-D-ribose (Methanolysis) a-Pyranoside formed first followed by P-pyranoside then p-furanoside and oc-furanoside (furanosides only minor products) Mechanism probably quite different to that of D-ribose first step may be direct displacement at C-1 of the six-membered, sulphur-containing ring 20)... 

A. Fleetwood and V. Hughes, Convenient synthesis of 2,3-0-isopropylidene-5-thio-D-ribose and 5-thio-D-ribose synthesis of l,4-anhydro-2,3-0-isopropylidene-u-D-ribo-pyranose and l,4-anhydro-2,3-0-isopropylidene-5-thio-u-D-ribopyranose, Carhohydr. Res., 317 (1999) 204-209. 

Thio-D-ribose (20) was first reported by Clayton and Hughes [44,45], an improved s)mthesis from D-ribono-1,4-lactone was published in 2002 [46]. Isopropylidene acetals [47] as well as 1,4-anhydro derivatives thereof [48] have also been made available. 

Conversion of tetra-0-acetyl-/3-D-ribopyranose into methyl 1-thio-/3-D-ribopyranoside, by the action of methanethiol and zinc chloride, with subsequent deacetylation, is accompanied by the formation of substantial proportions of methyl l,5-dithio-j8-D-ribopyranoside (55) and 4-S-methyl-4-thio-L-lyxose dimethyl dithioacetal (53), plus a trace of 5-S-methyl-5-thio-D-ribose dimethyl dithioacetal (56). Although similar treatment of tetra-O-acetyl-jS-D-ribofuranose for a short time produced the expected methyl 1-thio-jS-D-... 

Hughes and his co-workers have reported the preparation of three types of thio-sugar derivatives. The strong preference of 5-thio-D-ribose and 5-thio-D-xylose for ring-closure on to sulphur is shown by the formation of the strained 1,2 3,4-diacetals (188) and (189) in the reactions with acetone and 2,2-dimethoxy-... 

Several 4- and 5-thioaldoses have now been prepared. Both 4-thio-D-and -n-ribose form 4-thiofuranosides in hot acidic methanol.16 In contrast, 5-thio-L-arabinose and 5-thio-L-idose form 5-thiopyranosides.16 160 In these... 

Hodge et al. (45) discussed mechanisms for formation of methyl furanones and related substances from Amadori compounds. They have been produced by heating D-ribose and D-ribose phosphate with ammonia (46 47). Hicks and Feather (48) demonstrated that the Amadori compound 1-benzylamino-l-deoxy-D-threo-pentulose dehydrates to 4-hy-droxy-5-methyl-3(2H)-furanone and it has also been identified as a degradation product of L-ascorbic acid. This compound is believed to be formed from ribose-5-phosphate, and gained prominence when it was isolated from beef by Tonsbeck et al. (49). It became more apparent as a precursor of meat flavor when Van den Ouweland and Peer (50) reacted it and its thio analog with HaS to produce a number of sulfur compounds, some of which had meaty odors. 

Further examples of rearrangements involving cyclic sulphonium ions have been reported. Thus 2,3,5-tri-0-methyl-4-0-toluene-/>-sulphonyl-D-ribose diethyl dithioacetal (184) and dibenzyl dithioacetal (185) gave 4- S -ethyl-2,3,5-tri-0-methyl-4-thio-L-lyxose (186) and benzyl 2,3,5-tri-0-methyl-l,4-dithio-a-L-lyxo-furanoside (187) (Scheme 46) when heated either in aqueous pyridine or with sodium iodide in acetone similar rearrangements to the 4-thiofuranosides were observed with 2,3,5-tri-0-methyl-4-0-toluene-p-sulphonyl-D-xylose and -lyxose... 

The promastigotes of donovani were incubated for 24 hours at a concentration of about 10 cells/ml in the presence of (4-3 S)TPP, (4- 5s)tppr, and (U-l C-ribose)TPPR. A radioactive metabolic product was identified which had a retention time and ultraviolet absorption spectrum identical to authentic 4-thio-pyrazolo(3,4-d)pyrimidine ribonucleoside-5 -phosphate (TPPR-MP). 

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