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Oligosaccharide Analogues of Polysaccharides, Part 16, Cross‐Coupling of Partially Protected Dialkynyl Monosaccharides
Author(s) -
Bohner Tanja Verena,
Beaudegnies Renaud,
Vasella Andrea
Publication year - 1999
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/(sici)1522-2675(19990210)82:2<143::aid-hlca143>3.0.co;2-0
Subject(s) - monosaccharide , chemistry , monomer , yield (engineering) , dimer , substituent , nitrobenzene , coupling (piping) , stereochemistry , organic chemistry , polymer , materials science , metallurgy , catalysis
The dependency of the cross‐coupling of orthogonally C ‐protected dialkynyl monosaccharides on the nature of the coupling partners has been studied. The required dialkyne 5 was synthesized from levoglucosan in six steps and 39% overall yield and transformed into 7 , 10 , 12 , 13 , and 14 by orthogonal C ‐deprotection and bromination ( Scheme 1 ). Optimization of the conditions of their cross‐coupling to 16 showed that yields were higher for the coupling of the propargylic bromoalkyne 10 than for the homopropargylic bromoalkyne 14 ( Scheme 2 ). Deprotection of 16 gave the nano‐crystalline dimer 20 . To obtain more highly crystalline products, the monomers 7 and 13 were coupled with 1‐iodo‐4‐nitrobenzene to the arylated monomers 21 and 24 ( Scheme 3 ). The 4‐NO 2 C 6 H 4 substituent lowered the yield of the dimerizations to the mono‐ and diarylated dimers 26 – 28 ( Scheme 4 ) but had no effect on crystallinity.