Patent ID: 8598362

Claim:
A process for the preparation of a compound of formula (III): or a salt thereof, comprising the step of reacting a compound of formula (II): or a salt thereof, with a sulfonating agent, wherein: Q represents a thiol-reactive moiety; E represents a linear, branched or cyclic alkyl, alkenyl or alkynyl bearing 1 to 10 carbon atoms, a phenyl group, a three to six membered heterocycloalkyl group or a five or six-membered heteroaromatic group, containing 1, 2 or 3 heteroatoms selected from O, N or S; F is an optional moiety that has the same definition as E; or when G is absent, F and R 1 together with the carbon atom from which they are attached can form a three to seven membered cycloalkyl group; G is absent or represents -G′-(OCH 2 CH 2 ) n —, -G′-(CH 2 —CH 2 —O) n — or -(AA) m -; G′ is absent, —C(═O)—NH— or —NH—C(═O)—, AA represents an amino acid residue; R 1 is —H or a linear, branched or cyclic alkyl, alkenyl or alkynyl bearing 1 to 10 carbon atoms; n is 0 or an integer from 1 to 24; and m is 0 or an integer from 1 to 6.