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Stereoselective 1,2‐ cis Glycosylation of 2‐ O ‐Allyl Protected Thioglycosides
Author(s) -
Aloui Mahmoud,
Chambers David J.,
Cumpstey Ian,
Fairbanks Antony J.,
Redgrave Alison J.,
Seward Christopher M. P.
Publication year - 2002
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20020603)8:11<2608::aid-chem2608>3.0.co;2-4
Subject(s) - chemistry , glycosylation , intramolecular force , glycosyl , glycosyl donor , stereoselectivity , yield (engineering) , stereochemistry , acceptor , combinatorial chemistry , organic chemistry , catalysis , biochemistry , materials science , metallurgy , condensed matter physics , physics
The technique of intramolecular aglycon delivery (IAD), whereby a glycosyl acceptor is temporarily appended to a hydroxyl group of a glycosyl donor is an attractive method that can allow the synthesis of 1,2‐ cis glycosides in an entirely stereoselective fashion. 2‐ O ‐Allyl protected thioglycoside donors are excellent substrates for IAD, and may be glycosylated stereoselectively through a three‐step reaction sequence. This sequence consists of quantitative yielding allyl bond isomerisation, to produce vinyl ethers that can then undergo N ‐iodosuccinimide mediated tethering of the desired glycosyl acceptor, and subsequent intramolecular glycosylation, to yield either α ‐glucosides or β ‐mannosides accordingly. Although attempted one‐pot tethering and glycosylation is hampered by competitive intermolecular reaction with excess glycosyl acceptor, this problem can be simply overcome by the use of excess glycosyl donor. Allyl mediated IAD is a widely applicable practical alternative to other IAD approaches for the synthesis of β ‐mannosides, that is equally applicable for α ‐ gluco linkages. It is advantageous in terms of both simplicity of application and yield, and in addition has no requirement for cyclic 4,6‐protection of the glycosyl donor.