A compound of formula (I), wherein R1 is hydrogen or a hydroxyl protecting group; and R2 and R3 are same or different and are independently selected from halogen or —O—SO2—X; wherein X is —C1-C4 alkyl; C1-C4 alkyl substituted with one or more halogen; or substituted or unsubstituted phenyl wherein said phenyl substituent is selected from halogen, nitro and C1-C4 alkyl; provided that when R3 is bromine, X is not p-toluoyl; and a process for the preparation thereof.