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Palladium‐Mediated Cyclization on Carbohydrate Templates Synthesis of Enantiopure Annelated Tricyclic Compounds
Author(s) -
Sinou Denis,
Bedjeguelal Karim
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(200012)2000:24<4071::aid-ejoc4071>3.0.co;2-1
Subject(s) - chemistry , palladium , enantiopure drug , substituent , alkylation , intramolecular force , aryl , medicinal chemistry , anomer , bromide , alkoxy group , stereochemistry , leaving group , organic chemistry , catalysis , enantioselective synthesis , alkyl
Various bromo unsaturated carbohydrates 2−4 have been prepared from ethyl and aryl 4,6‐di‐ O ‐acetyl‐2,3‐dideoxy‐α‐ D ‐ erythro ‐hex‐2‐enopyranoside by deacetylation, followed firstly by monosilylation with TBDMSCl and then by alkylation with 2‐bromobenzyl bromide or 1‐bromo‐bromomethylcycloalkene. The N ‐, C ‐, and O ‐analogues 6−8 were prepared by palladium‐mediated alkylation of the carbonate 5 with TsNHCH 2 −C 6 H 4 ‐ o ‐Br, (CO 2 Me) 2 CH−C 6 H 4 ‐ o ‐Br, and HOC 6 H 4 ‐ o ‐I, respectively. The threo analogue 10 was obtained using the same methodology as for 2 , after inversion of configuration at C‐4 by means of a Mitsunobu reaction. Treatment of the unsaturated carbohydrates 2−4 , 6−8 , and 10 with a catalytic amount of Pd(OAc) 2 /PPh 3 in DMF in the presence of Bu 4 NHSO 4 and NEt 3 afforded the annelated tricyclic compounds 11−13 and 15−18 in good yields when the anomeric substituent was the p ‐ tert ‐butylphenyl group, via an intramolecular Heck reaction followed by a β‐alkoxy‐palladium elimination