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Oligosaccharide Analogues of Polysaccharides, Part 22 , Synthesis of Cyclodextrin Analogues Containing a Buta‐1,3‐diyne‐1,4‐diyl or a Butane‐1,4‐diyl Unit
Author(s) -
Hoffmann Barbara,
Zanini Diana,
Ripoche Isabelle,
Bürli Roland,
Vasella Andrea
Publication year - 2001
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(20010613)84:6<1862::aid-hlca1862>3.0.co;2-z
Subject(s) - chemistry , anomer , stereochemistry , moiety , glycosyl donor , glycosidic bond , cyclodextrin , oligosaccharide , yield (engineering) , glycosyl , organic chemistry , materials science , metallurgy , enzyme
The peracetylated hexaamylose (maltohexaose) 18 was obtained by an improved acetolysis of cyclomaltohexaose ( α ‐cyclodextrin, α ‐CD, 16 ), and transformed into the benzyl‐ and 4‐chlorobenzyl‐protected thioglycosides 22 and 23 , respectively ( Scheme 2 ). Sequential chain elongation of 22 and 23 by glycosidation of the C ‐ethynylated glucosides 9 and 11 gave the α ‐anomeric heptaglycosides 24 and 26 , respectively, and their anomers 25 and 27 ( Scheme 3 ). These were transformed into the glycosyl acceptors 28 , 30 , and 31 . Glycosidation of 28 and 30 by 13 and 15 , respectively, led to the benzyl‐protected octasaccharides 32 ( αα 5 α ) and 33 ( βα 5 α ), and to the chlorobenzylated analogues 34 ( αα 5 α ) and 35 ( βα 5 α ), while glycosidation of 31 led to the 4‐chlorobenzyl‐protected analogues 36 ( αα 5 β ) and 37 ( βα 5 β ) ( Scheme 4 ). Hay coupling of O ‐Bn‐ and O ‐Ac‐protected linear octaoses 32 ( αα 5 α ) and 33 ( βα 5 α ) led to the cyclooctaamylose ( γ ‐cyclodextrin) analogues 38 and 43 , respectively ( Scheme 5 ). Similarly, the 4‐chlorobenzyl‐protected analogues 34 and 35 gave 39 and 44 , and the anomeric linear precursors 36 and 37 provided the cyclootaamylose analogues 48 and 50 , respectively ( Scheme 6 ). The influence of the constitution and configuration of the linear precursors on the rate and yield of the cyclisation was relatively weak. Deprotection and hydrogenation of 38 and 43 yielded the γ ‐CD analogues 42 ( αα 5 α ) and 47 ( βα 5 α ), where one glycosidic O‐atom is replaced by a butanediyl group, while FeCl 3 ‐promoted dechlorobenzylation of 39 and 44 did not affect the butadiyne moiety and afforded the acetyleno γ ‐CD's 40 ( αα 5 α ) and 45 ( βα 5 α ), respectively. Similarly, deprotection of 48 and 50 afforded the acetyleno γ ‐CD analogues 49 ( αα 5 β ) and 51 ( βα 5 β ), respectively, which contain one butanediyl moiety instead of a glycosidic O‐atom. MM3* Force‐field calculations evidence the strong influence of the configuration and constitution of the new γ ‐CD analogues on the shape of the cavity.