Consider the constitution of the open-chain sugar shown. Counting configurational stereoisomers only (all stereocentres treated as independent, no meso forms arise), how many stereoisomers does this constitution have? Give your answer as an integer.

Numerical answer type, tolerance 0.5.

Answer: 16

The open-chain aldohexose has four stereocentres (C-2 to C-5) and no symmetry, so the number of stereoisomers is

2^{4} = 16

. This was confirmed by enumeration with RDKit. The sugar is D-glucose, one of eight D and eight L aldohexoses.