Insulin-like, and insulin-antagonistic, carbohydrate derivatives. The synthesis of aryl and aralkyl d-mannopyranosides and 1-thio-d-mannopyranosides

α-d-Mannose derivatives as models designed for selective inhibition of Golgi α-mannosidase II

“…A glycosylation of the corresponding alcohols and thioalcohols with mannose pentaacetate under a promotion of Lewis acid (BF 3 $OEt 2 ) was used in this study for a coupling of the donor 1 with benzyl and 2-phenylethyl thioalcohols, yielding thioglycosides 2 and 3 [25]. The synthesis of other compounds (14e20) depicted in Fig.…”

“…The deacetylation under mild conditions using K 2 CO 3 in MeOH with subsequent purification by column chromatography, afforded the target compounds 4 [25], 5 [25], 8, 9, 12 and 13. Transformation of the thioglycosides to the sulfoxides and the sulfones was clearly evident from their 1 H and 13 C NMR spectra. In 1 H NMR spectra signals for H-1 of major acetylated sulfoxide and sulfone were upfield shifted in comparison with that of the starting thioglycoside; and the signal of the sulfoxide appeared at the lowest chemical shift from these sulfur-containing compounds.…”

“…Although it is known that sixmember ring structures are not potent inhibitors of GM [1], the main goal of our study was to modify the aglycone unit of the mannosides to improve their selectivity directed toward GM. For their preparation we used the structural motif of an optimized synthesis described in our previous paper [25]. Moreover, a-Dmannose moiety is essential part of the native substrate of GM and its binding with the Zn 2þ ion co-factor at the active site of dGM has been previously characterized by crystallographic measurements [21,22].…”

Synthesis of Thioglycosides by Tetrathiomolybdate‐Mediated Michael Additions of Masked Thiolates

“…Thus, methyl 6-bromo-6-deoxy-α-dglucopyranoside (12), [22] obtained from methyl α-d-glucopyranoside 11 in a reaction with PPh 3 , and CBr 4 in pyridine, was treated with ammonium tetrathiomolybdate (2) (2 equiv.) in the presence of methyl vinyl ketone in water as the solvent to give the Michael adduct 14 as the only product in good yield (82%) (Scheme 3).…”

“…[9] The most commonly used methods include the use of isothiourea derivatives of sugars (in turn derived from the glycosyl halides and thiourea) as precursors, [10] treatment of glycosyl halides with thiolate anions, [11] or the reaction between a 1-thioglycopyranose and an alkyl halide. [12] Other methods are based on Lewis acid catalyzed glycosylation of thiols. By this approach, thioglycosides have been prepared by starting from 1,2-trans-glycosyl esters, [13] trichloroacetimid-Further, the utility of this one-pot reaction in aqueous medium has been exemplified through the use of ammonium tetrathiomolybdate [(NH 4 ) 2 MoS 4 ; 2].…”