The enantiopure ketone shown (stereocentre fixed) is reduced with sodium borohydride, followed by work-up. How many stereoisomeric alcohols can form? (Count configurational isomers with the existing stereocentre retained.)

(S)-3-Methylcyclohexanone has one fixed stereocentre. Reduction creates a second one at C-1 bearing OH, which may be cis or trans to the methyl group. The two products, cis- and trans-3-methylcyclohexanol, are diastereomers, so 2 stereoisomers form. RDKit enumeration with the methyl centre fixed gives 2.