Many alternative synthetic routes were investigated. The second synthesis that was carried out at scale is detailed in Scheme 2 and relied on the enzymatic resolution of the racemic α-hydroxy ester 5. This route was successfully carried out by a contract manufacturer and provided 19 kg of 4. Initial calculations predicted this route could supply 3 at a suitable cost. However, the initial calculated cost was not realised, partly because of the cost associated with the ...
