A process for preparing an optically active compound of formula (II) or a salt thereof
where * indicates a stereogenic centre; and R
1
and R
7
are as defined in the specification, which process comprises the acid hydrolysis of an optically active compound of formula (IV)
where R
5
and R
6
are as defined in the specification, recovering the resultant optically active compound of formula (II) as a salt, and thereafter if desired, converting the salt to a compound of formula (II).
The process is suitable for the preparation of; for instance, intermediates for pharmaceutical compounds. Certain novel intermediates are also disclosed and claimed.