Acylation glycoside synthesis

An interesting appHcation of the rhodium-catalyzed cyclotrimerization of diynes with alkynes to the synthesis of C-acyl glycosides has been reported, wherein ethynylglycal 52 (Eq. 15), as well as diethynylglucose derivative 54 (Eq. 16), are employed to give the corresponding adducts 53 and 55, respectively [38]. 

Stoicheiometric RuOyCCl was also used to oxidise several furanoses, partially acylated glycosides and l,4 3,6-dianhydrohexitols [317] pyranosides to pyrano-siduloses [313] methyl 2,3,6-tri-O-benzoyl-a-D-glucopyranoside and its C-4 epimer to the a-D-xy/o-hexapyranosid-4-ulose (Table 2.3) [317], and methyl 2,3,6-trideoxy-a-D-e 7f/tro-hexapyranoside to the -a-D-,g/yceri9-hexa-pyranosid-4-ulose, an intermediate in the synthesis of forosamine [318], It was also used to oxidise benzyl 6-deoxy-2,3-0-isopropylidene-a-L-mannopyranoside to the a-L-/yxo-hexapyranosid-4-ulose [319] and for oxidation of isolated secondary alcohol functions, e.g. in the conversion of l,6-anhydro-2,3-0-isopropylidene-P-D-man-nopyranose to the-P-D-/yxo-hexa-pyranos-4-ulose mannopyranose (Fig. 2.16, Table 2.3 [20, 320, 324]). 

Finally, Kren and coworkers have proposed the use of selectively acylated glycosides to be used as acceptors in a bi-enzymatic approach to the synthesis of di- and trisaccharides exploiting lipases/proteases and glycosidases (for instance, 6-0-acetyl-N-acetyl-D-glucosamine, 14, to give the corresponding chitobiose derivative 15) [44]. 

K. Jansson, S. Ahlforts, T. Frejd, J. Kihlberg, G. Magnusson, J. Dahmdn, G. Noori, and K. Stenvall, 2-(TrimethyIsiIyl)ethyI glycosides. Synthesis, anomeric deblocking, and transformation into 1,2-trans 1-O-acyl sugars, J. Org. Chem. 53 5629 (1988). 

Since the acylated sugars are of such importance as intermediates in the syntheses of glycosides, constants for the poly-acetates and -benzoates have been collected in Tables VIII to X. Optical rotations are, again, usually given for solutions in chloroform. To the best of our knowledge, there is no recent compilation of constants for these compounds. For the other important class of intermediates in glycoside synthesis, the 0-acylglycosyl halides, the reader is referred to the Tables in a previous review in this Series. ... 

Scheme 20. Isonitriles in the radical synthesis of 1-acyl glycoside derivatives...

N-Glycosyl-N-hetepocyclics from acyl glycosides Nucleoside fusion synthesis... 

Ryan DA, Gin DY (2008) Glycoside synthesis from 1-oxygen substituted glycosyl donors hemiacetals and O-acyl/carbonyl derivatives. In Demchenko AV (ed) Handbook of chemical glycosylation. Wiley-VCH, Weinheim, pp 95-143... 

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