Glycosyl isocyanate

Alkyl and glycosyl isocyanates and isothiocyanates are produced in good yield under phase-transfer catalytic conditions using either conventional soluble catalysts or polymer-supported catalysts [32, 33]. Acyl isothiocyanates are obtained under similar conditions [34]. A-Aryl phosphoramidates are converted via their reaction with carbon disulphide under basic conditions into the corresponding aryl isothiocyanates, when the reaction is catalysed by tetra-n-butylammonium bromide [35]. 

Retrosynthetic analysis for the synthesis of a key building blockl for such a glycopeptide mimics is shown in Figure 10. It was envisaged that the synthesis of I could be achieved by a coupling reaction of the glycosyl isocyanates II and the amino acid derivatives III, and initial work focused on the synthesis of the glycosyl isocyanates IV. 

Sugar derivatives having isothiocyanate groups on the various carbon atoms were used for the synthesis of trehazoline and its analogues. Thus, the glycosyl isocyanate, where the isothiocyanate group is at the anomeric center, as required for the synthesis of trehazolin 2, was readily synthesized by reaction of the glycosyl donor 6 with a metal isothiocyanate (Scheme 2).23... 

See Tables of Compounds in Ellis and Honeyman for data on glycosyl isocyanates and isothiocyanates, and glycosyl-urethans, -thiourethans, -hydantoins, -thiohydantoins, and related compounds. 

The iV-glycosylated analogues (32) and (33) of furacilin and benaazon VII were prepared by condensation of glycosyl isocyanates and isothiocyanates, respectively, with 5-nitrofurfural hydrazone followed by deacetylation. ... 

The glycosyl ureide and thioureide obtained through the isocyanate and isothiocyanate routes were prepared from tetra-O-acetyl-a-D-glucopyranosyl bromide. The glycosyl ureides derived from this source are identical with those prepared by the acid-catalyzed condensation of D-glu-cose with urea and with thiourea. 

Glyoosyl isocyanates and isothiocyanates, amination of, 220 Glycosyl thioureides, 215-217 Glycosyl ureides, 216-218, 227, 228 Glyoxal, 317, 318, 328 —, phenyl-, 297... 

Another method for synthesis of useful derivatives of L-acosamine and L-daunosamine from rhamnal 23 was based on addition of chlorosulfonyl isocyanate to 2,3-unsaturated pyranosides 73 [66,67]. Since the anomeric alkyl substituent in this reaction ends up as the carbamate ester, aUyl glycoside securing easy deprotection was chosen for elaborating this reaction into large laboratory scale technical process. Method development for acosam-inal derivative 74 involved multiparameter optimization of the isocyanate addition step by exploration of the reaction response surface. The final daunosaminyl glycosylation synthon 76 was obtained in overall 35% yield (Scheme 12) [68]. 

With this system and the building blocks 19,28, and 45 shown in the scheme up to a branched hexasaccharide W-glycan was successfully obtained (11 steps on solid phase, 19% overall yield 86% per step) (see 34). This was a major improvement over the results reported in Scheme 4. A careful study of this reaction sequence revealed that the second glycosylation step is incomplete, thus leading also to byproduct formation (48). Therefore, a capping step of unreacted hydroxy groups based on benzoyl isocyanate reaction was introduced (25). As expected and shown in Scheme 11, this way clean product formation could be gained, however the overall yield was not increased. 

Glycosylurea and thiourea derivatives, e.g. (19), were synthesized by condensation of alkyl isocyanates and isothiocyanates respectively, with jS-D-glucopyranosylamine and fi-lactosylamine, as non-ionic detergents of particular interest for extraction of membrane proteins. Various l-( -D-glycosyl)-derivatives of diphenylhydantoin and hydrochlorothiazide were synthesized in an attempt to enhance the hydrophilicity and biological activity of these materials. Conformation analysis and X-ray structures of some 1,2- and 1,3-fused glycosylamine derivatives are included in Chapters 21 and 22. 

Glycosyl azides, such as the -D-ribosyl derivative (24), have been converted to the corresponding formamlde, isocyanide, and isocyanate derivatives as indicated in Scheme 5." ... 

Other methods for modifying polymers with carbohydrates via the postpolymerization technique include the photo-grafting of poly(ethylene terephthal-ate) (PET) fibers with glycosyl azides [218] and the use of carbohydrates bearing isocyanate [219] or aldehyde [220] groups, which react efficiently with polymers bearing pendant amino residues. 

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