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Stereoselective Synthesis of carba ‐ and C ‐Glycosyl Analogs of Fucopyranosides
Author(s) -
Carpintero Mercedes,
Jaramillo Carlos,
FernándezMayoralas Alfonso
Publication year - 2000
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200004)2000:7<1285::aid-ejoc1285>3.0.co;2-z
Subject(s) - chemistry , stereoselectivity , carbanion , regioselectivity , stereochemistry , anomer , electrophilic addition , electrophile , medicinal chemistry , organic chemistry , catalysis
Fucopyranoside analogs with methylene groups instead of endo ‐ or exo ‐anomeric oxygens, carba ‐ and C ‐fucopyranosides, respectively, were synthesized. For the synthesis of 5a‐ carba ‐ L ‐fucose ( 1 ) two approaches were studied, which shared a common cyclitol building block ( 8 ), obtained from a SmI 2 ‐promoted carbocyclization of a D ‐mannitol derivative. The first route made use of a Stork radical cyclization onto a conduritol derivative 13 as the key step, which failed to give the silyl ether ring. The second route furnished the target 1 , and involved regioselective elimination of a cyclic sulfate 9 , and stereoselective hydrogenation of a double bond, controlled by substitution on the substrate. For the synthesis of 1‐ C ‐fucopyranosides ( 37 , 38 , and 42 ) a new method based on the use of fucosyl phenyl sulfoxides ( 35 and 41 ) was employed. An anomeric carbanion is generated through phenylsulfinyl‐lithium exchange, which reacted with electrophiles with retention of configuration at the anomeric center. The required fucosyl sulfoxides were prepared from L ‐fucose by highly stereoselective thioglycosylation reactions.