Acylation protecting groups

The B SE group was used for intemucleotide protection and is removed with ammonia, also used to remove A -acyl protective groups. Compared with the methylsulfonylethyl group, the B SE group has better solubility properties for solution phase synthesis. ... 

P Sjolin, M Eloffsson, J Kihlberg. Removal of acyl protective groups from glyco-peptides base does not epimerize peptide stereocenters, and P-elimination is slow. J Org Chem 61, 560, 1996. 

The synthetic plan is shown in Scheme 10. When used in combination with a glycosyl acceptor 17, the glucobiosyl donor 33 (which carries different kinds of acyl protective groups on 0-4. and 0-6 ), may be suitable for the preparation not only of 30 but also of other intermediates carrying different functional groups at C-6 of the nonreducing-end glucopyranosyl residue of 30. 

The requirement for an acyl protecting group represented a major drawback for an asymmetric hydrogenation approach in the synthesis of sitagliptin, since it would likely introduce additional chemical steps in the sequence for protection and deprotection. The ideal situation would be to perform the asymmetric hydrogenation on an unprotected enamine. Unfortunately, this transformation was unprecedented when we started the development work on sitagliptin [22]. 

Thus, sucrose, ubiquitous in everyday life, is still an elusive target substance in the chemical laboratory. Perhaps acyl-protecting groups in the glucosyl acceptor could stabilise the acetal and the anomeric linkage enough to enable sucrose to be finally produced in a simple procedure. 

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