Anomeric O-acylation of Kdo using alkyl and aryl isocyanates.

Carbohydrate research (2005-10-04)
Tsuyoshi Ichiyanagi, Ryohei Yamasaki
ABSTRACT

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.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
4-(Chloromethyl)phenyl isocyanate, 97%