Abstract: A pyranose ring contraction of ethyl 1-thio-β-d-galactopyranosides has been discovered that proceeds with retention of aglycon under mildly acidic conditions (aq TFA in CH2Cl2). Key factors for success of this rearrangement are the presence of bulky silyl (TIPS or TBDPS) substituents at both O-2 and O-3 and a free hydroxy group at C-4 (derivatives with acid-labile protective groups at O-4 will also engage in this reaction). The rearrangement cleanly proceeds for 2,3-di-O-TIPS derivatives with two hydroxy groups at C-4 and C-6, acid-labile TES groups at O-4 and O-6, or one acyl substituent (Bz, ClAc) at O-6. A possibility to switch the direction of the debenzylidenation reaction in 4,6-O-benzylidene-2,3-di-O-TIPS/TBDPS derivatives by the choice of an acid (TFA, which cleanly gives furanose, versus AcOH, which cleaves benzylidene acetal only) may present an advantage in the divergent synthesis of selectively protected glycosyl donors (either in furanose or pyranose form) useful for the synthesis of biologically important oligosaccharides.

Cite: Abronina P.I. , Malysheva N.N. , Litvinenko V.V. , Zinin A.I. , Kolotyrkina N.G. , Kononov L.O.
A Ring Contraction of 2,3-Di-O-Silylated Thiopyranosides To Give Thiofuranosides under Mildly Acidic Conditions
Organic Letters. 2018. V.20. N19. P.6051-6054. DOI: 10.1021/acs.orglett.8b02424 WOS Scopus OpenAlex

Identifiers:

Web of science:	WOS:000447118200015
Scopus:	2-s2.0-85053638427
OpenAlex:	W2891957180

Citing:

DB	Citing
OpenAlex	22
Web of science	19
Scopus	20

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