Patent ID: 7297787

Claim:
A process wherein a N 6 -substituted aminopurine ribofuranose nucleoside of formula (I): is prepared by reacting a 6-halopurine ribofuranose nucleoside of formula (II) with an amine of formula (III) H 2 N—R 1 (III) in the presence of CaCO 3 ; with acid added to the reaction mixture at the start of the reaction; wherein in formulae (I), (II), and (III): L is halogen; R 1 is hydrogen or a group selected from: (i) -(alk) n -(C 3-9 )cycloalkyl or -(alk) n -(C 3-9 )cycloalkenyl, said cycloalkyl or cycloalkenyl group being optionally substituted by one or more substituents selected from OH, halogen, C 1-6 alkyl, —C 1-6 alkoxy, C 2-6 alkenyloxy-, C 2-6 alkynyloxy-, and phenyl, wherein (alk) is C 1-3 alkyl and n represents 0 or 1, and said (alk) group may be optionally substituted by a C 3-6 cycloalkyl group; (ii) a phenyl group optionally substituted by one or more substituents selected from: halogen, OH, CF 3 , cyano, —C 1-6 alkyl, —C 2-6 alkenyl, —C 2-6 alkynyl, C 1-6 alkoxy-, —C 1-6 alkylOH, —CO 2 H, and —CO 2 C 1-6 alkyl; (iii) a C 4-7 aliphatic heterocyclic group containing at least one heteroatom selected from O, N and S, and optionally substituted by one or more substituents selected from: OH, —C 1-6 alkyl, —C 1-6 alkoxy, —CO 2 (C 1-4 )alkyl, —CO(C 1-4 )alkyl, —CO 2 aryl, and —CO 2 (alk) n (C 3-6 )cycloalkyl, wherein (alk) is C 1-3 alkyl and n represents 0 or 1; (iv) a straight or branched C 1-12 alkyl group optionally substituted by one or more groups selected from phenyl, halogen, hydroxy, and C 3-7 cycloalkyl, wherein one or more carbon atoms of the C 1-12 alkyl group may be optionally replaced by a group independently selected from S(=O) n (where n is 0, 1 or 2) and N; and (v) a fused bicyclic ring wherein A represents C 4-6 cycloalkyl or phenyl and B represents phenyl optionally substituted by C 1-3 alkyl, and the bicyclic ring is attached to the purine-6-amino moiety via a ring atom of ring A; R 2 is C 1-3 alkyl, C 1-3 alkenyl, C 1-3 alkoxy, halogen or hydrogen; R 3 is (i) hydrogen, (ii) C 1-6 alkyl optionally substituted by one or more halogens, (iii) C 1-6 alkylOCH 2 — where the alkyl chain is optionally substituted by one or more halogens, (iv) an acetylene group, or (v) a 5-membered heterocyclic group optionally substituted by: C 1-6 alkoxy-, —C 1-6 alkylO(CH 2 ) n — where n is 0-6, C 3-7 cycloalkyl, C 1-6 hydroxyalkyl, halogen, a —C 1-6 alkyl, —C 16 alkenyl, or —Cl 1-6 alkynyl group optionally substituted by one or more halogens; R 4 and R 5 independently are hydrogen, acyl, —C 1-6 alkyl or a suitable protecting group.