1-Thio-a-D-mannose

Glycosyl halides (7a-e) were stereoselectively transformed into l,2-tra s-thio-glycoses by i) (8a-d, 8j) a two-step procedure via the pseudothiourea derivatives [9,10a] the substitution of halide by thiourea is mostly a S l-type reaction since acetylated 1-thio-a-D-mannose (8b) was obtained from acetobromoman-nose (7b) [9cj ii) (8e-i) using thiolates in protic and aprotic solvents [10], or under phase transfer catalysis conditions [11]. Another approach involved the reaction of thioacetic acid with 1,2-trans-per-O-acetylated glycoses catalyzed with zirconium chloride [12]. The 1,2-trans-peracetylated 1-thioglycoses (8e-h) were obtained in high yield. No anomerized products could be detected in these reactions (Fig. 1). 

The branched cyclodextrins (CDs, 17a, 17b) and their analogues with /J-D-galactosyl and a-D-mannosyl residues (17c, 17d) have also been prepared under mild conditions by the approach depicted in Scheme 6 [24,25]. Selective in situ S-deacetylation and activation was obtained by treatment of peracetylated 1-thioglycoses (10a, 8e, 8g) by cysteamine in the presence of dithioerythritol in HMPA [26]. This method was very efficient for the synthesis of branched CDs (17a) (80%), (17b) (60%), and (17c) (85%) when the acceptor molecule (15b) bearing primary iodide was used. However, peracetylated 1-thio-a-D-mannose (8 f) failed as a donor under these conditions, but tetra-O-acetyl-l-thio-a-mannose (8b) afforded the expected CD (17d) in high yield (83%). 

Efficient syntheses of trehazolamine (5) starting from D-mannose (Scheme 15)79 have been readily achieved by deacetylation of phenyl 1-thio-a-D-mannopyranoside (109),80 followed by monoacetonation under kinetic conditions to give 110. Regio-selective benzylation of the equatorial hydroxyl group of 110 gave 111, whose... 

Fig. 13.—A Agar diffusion of immune sera (Se), 1-thio-D-mannose antibodies (A ), and anti-BSA antibodies (A2) against Man-S-BSA (/) and BSA (2). B Agar-diffusion plate of anti-Man-S-antibodies and antibodies oxidized by peroxypropanoic acid for 0, 4, and 8 h. C, D, E, and F Hapten inhibition by agar diffusion, A = purified anti-Man-S antibodies I = antibodies + p-nitrophenyl 1 -thio-a-D-mannopyranoside 12 = antibodies + D-mannose I3 = antibodies + ethyl 1-thio-a-o-mannoside 1 to 6, outer wells contain decreasing concentration of Man-S-BSA. (Reprinted with permission from Journal of Protein Chemistry, Volume 9, J. H. Pazur, B. Liu, Nan Q Li, and Y. C. Lee, pp. 143-150, copyright 1990 Journal of Protein Chemistry.)...

Ethyl 2-0-benzoyl-1-thio-a-L-rhamnopyranoside, T-86 Ethyl 4-O-benzoyl-l-thio-a-L-rhamnopyranoside, T-86 Ethyl 4-0-benzyi-2-0-methyl-l-thio-a-D-rhamnopyranoside, T-86 Ethyl 4-O-benzyl-l-thio-a-D-rhamnopyranoside, T-86 Ethyl 2,4-di-O-benzoyl-l-thio-a-L-rhamnopyranoside, T-86 Ethyl 2,3-O-isopropylidene-l-thio-a-D-rhamnopyranoside, T-86 Ethyl rhamnoside a-L-Furanose-/orm, E-27 Ethyl I-thicHX-L-rhamnopyranoside, T-86 Ethyl I-thio-p-L-rhamnopyranoside, T-86 Ethyl 2,3,4-tri-O-acetyl-l-thio-a-L-rhamnopyranoside, T-86 Ethyl 2,3,4-tri-0-acetyl-l-thio-(3-L-rhamnopyranoside, T-86 a-D-Fucopyranosyl-(l ->2)-a-L-rhamnopyranosyl-(l ->3)-i>mannose, F-159... 

The inhibition of precipitin formation by 1-thio-D-mannose and derivatives is shown in the results recorded in Plates C, D, E, and F of Fig. 13. The sulfur derivatives, p-nitrophenyl 1-thio-D-mannopyranoside (well Ii) and ethyl 1-thio-D-mannopyranoside (well I3), caused a marked decrease in the amount of precipitin formation, in comparison to that obtained with the native antibodies (Well A,). However, mannose did not decrease the amount of precipitin formation (well I2). This compound did not bind to the combining site of the antibody. Apparently, the thio group at position 1 of the mannose is required for the binding to occur. 

Thio-D-mannose 7, discovered as a metabolite of the marine sponge Clathria pyramida (Lendenfeld), is still unique as the only example of a 5-thioaldopyranose occurring in nature [45]. Shortly after its discovery, a synthesis from methyl 2,3 5,6-di-0-isopropylidene-a-D-mannofurano-side was reported [46], which essentially followed the principle of the approach depicted in Scheme 9.1. Earlier, 5-thio-D-mannose had been available by molybdate catalyzed epimerization [47,48] of 5-thio-D-glucose 10 [37]. 

It is highly probable that the initial step in the overmercaptalation of 27 involves formation of a 2,3-acyloxonium ion however, formation of the 1,2-episulfonium ion 28 as an intermediate in the replacement of the 2-hydroxyl group has been established130 through the conversion of 27 into 3,4,5,6-tetra-0-benzoyl-2-S-ethyl-2-thio-D-man-nose ethyl phenyl dithioacetal (34) by the action of benzenethiol and an acid catalyst. The presence of an ethylthio group on C-2 in 34 was further established by conversion of 34 into 3,4,5,6-tetra-O-benzoyl-2-S-ethyl-2-thio-D-mannose dimethyl acetal. 

L-arabinose. A paper-chromatographic study of the mercaptalation reaction with n-galactose, D-glucose, and D-mannose confirmed that almost complete conversion to the dithioacetal occurred within 5 minutes, but, after several hours, an equilibrium was set up in which two 1-thio-glycosides, probably the anomeric pyranosides, the dithioacetal, and the free aldose were all present the 1-thioglycoside was particularly favored with the D-mannose structure. 3-Amino-3-deoxy-D-mannose reacted (qualitatively) similarly to D-mannose, but more slowly, probably because of the polar influence of the amino group. 

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