Anomeric O-acylation of Kdo using alkyl and aryl isocyanates.
To develop a convenient method for the preparation of an alpha-Kdo derivative carrying a functional spacer at the reducing end, we examined anomeric O-acylation using Kdo and halogenated alkyl/aryl isocyanates as nucleophile and electrophiles, respectively. Reaction of a Kdo derivative with 2-chloroethyl isocyanate in the presence of DMAP gave an alpha-spiro product (82%) and an alpha-Kdo derivative of a dimeric isocyanate adduct (10%). Similar reaction with 4-(chloromethyl)phenyl isocyanate gave only the corresponding alpha-spiro product (81%). The NMR data show that the pyranose rings of both the alkyl and aryl spiro products adopt the 5C2 conformation. Thus, we accomplished alpha-selective anomeric O-acylation by coupling the Kdo derivative with alkyl and aryl isocyanates.
Ichiyanagi
Tsuyoshi
T
Department of Biochemistry and Biotechnology, Tottori University, Tottori 680-8553, Japan.
Yamasaki
Ryohei
R
D000215:Acylation; D000478:Alkylation; D002236:Carbohydrate Conformation; D007202:Indicators and Reagents; D017953:Isocyanates / Q000737:chemistry*; D007700:Kinetics; D008958:Models, Molecular; D013400:Sugar Acids
D007202:Indicators and Reagents; D017953:Isocyanates; D013400:Sugar Acids; C002532:2-keto-3-deoxyoctonate