Fructose 6-thio

The extent to which the 4-thioaldoses are in the furanose forms is not certain. It has been claimed that 4-thio-L-ribose143 and 4-thio-D-glu-cose144 are completely in furanose forms, because they show no thiol absorption at 2550 cm-1 in their i.r. spectrum. This evidence is not convincing in the syrupy state, the composition may be different from that in dilute solution. The 13C-n.m.r. spectrum of a solution of 5-thio-D-fructose, however, shows141 only the signals of the two furanose forms, in the ratio of 11 89, at 25°. The -n.m.r. spectrum of a solution of... 

An aldolase-based strategy conveniently provided access to thioketoses with sulfur in the ring. For example, RAMA-catalyzed carbon-carbon bond formation of a 3-thioglycerinaldehyde with dihydroxyacetone phosphate gave 6-thio-D-fructose 36 [32] (Figure 9.8), also available by enzymatic isomerization of 6-thio-D-glucose or 6-thio-L-sorbose with glucose isomerase (EC 5.3.1.5 vide infra) [32,41]. 

Thio-D-fructofuranose (88) was prepared from 5-(9-tosyl-l,3-(9-isopropylidcnc-o -L-sorbopyranose (87) by the standard sequence of reactions shown in Scheme 26. The H and C NMR spectra of 88 in aqueous solution show only tlie signals of the furanose a and p anomers in the ratio of 11 89, whereas tlie NMR spectra of D-fructose in D2O show the presence of the -pyranose, -furanose, a-furanose, and a-pyranose in the ratio of 6 3 1 trace, respectively. Partial hydrolysis or methanolysis of 90, prepared from 1,6-di-O-tosyl-D-fructofuranose (89), gave 3,6-anhydro-l-deoxy-6-thio-D-oraZ)W7o (or D-yv/o)-hexulose (91). Nucleophilic attack of the ring sulfur atom on C-3... 

The resistance to iodide displacement of 1-O-sulfonyl derivatives of D-fructose and D-sorbose is well known,287 and selective displacement at C-6 of 2,3-0-isopropyIidene-l,6-di-0-p-tolylsulfonyl-D-fructo-furanose by sodium a-toluenethioxide in methanol gave 6-S-benzyl-2,3-0-isopropylidene-6-thio-l-0-p-tolylsulfonyl-D-fructofuranose in 74% yield.218... 

Fischer420 reported the preparation of mercaptals from carbohydrates the reaction can be applied to all aldoses and aliphatic thiols, but fails with thio-phenols and also with fructose and sorbose,421 so that it can be used to separate, e.g., glucose from a mixture with fructose and sorbose. 

In contrast to the facile reaction of 1,2 3,4-di-0-isopropylidene-6-0-p-tolylsulfonyl-a-D-galactose with ethanethiolate anion, the same displacement reaction on 2,3 4,5-di-0-isopropylidene-l-0-p-tolylsulfonyl-/3-D-fructose, which also has a primary p-tolylsulfonyloxy group, proceeds more slowly, to give l-(S-ethyl-2,3 4,5-di-0-isopropylidene-l-thio-/3-D-fructose. This behavior parallels the reactivities of the two sulfonate ester derivatives with iodide ion. Inspection of models indicates that rear-side approach to C-1 in the D-fructose derivative is subject to considerably more steric hindrance than the approach to C-6 of the D-galactose derivative. 

Penta-Ac l,3,4,6-Tetra-0-acetyl-5-S-acetyl-S-thio-D-fructose. 1-0,3-0,4-0,5-S, 6-0-Pentaacetyl-5-thio-D-fructose [53821-71-9]... 

S-Penta-Ac 1,3,4,5-Tetra-O-acetyl-6S-acetyl-6-thio-D-fructose [61403-00-7]... 

Thio-D-r/w o-pentulose (16) has been produced by stereospecific aldolase-catalyzed condensation of thioglycolaldehyde with hydroxyacetone monophosphate and subsequent treatment with phosphatase, as shown in Scheme 5, and 6-thio-D-fructose has been similarly obtained by use of racemic 3-thioglyceraldehyde. The preparation of an AZT 5 -lipidic sulfide is referred to in Chapter 20. 

Thio-D-fructose has been synthesized by three routes in which a thioacetyl group was introduced by direct displacements on L-sorbopyranose 5-sulphonates the best route is illustrated in Scheme 70. H N.m.r. spectroscopy indicated... 

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