The diketone shown is reduced with an excess of sodium borohydride, followed by work-up. Counting configurational stereoisomers of the diol constitution formed, including meso forms and counting enantiomers separately, how many stereoisomers does the diol have? Give the answer as an integer.

Numerical answer type, tolerance 0.5.

Answer: 3

Hexane-2,5-dione gives hexane-2,5-diol, which has two stereocentres related by a symmetry element of the constitution. The stereoisomers are (2R,5R), (2S,5S) and the meso (2R,5S) form, so there are 3 stereoisomers rather than 4. RDKit enumeration of the product confirms 3.

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The diketone shown is reduced with an excess of sodium borohydride, followed by work-up. Counting configurational stereoisomers of the diol constitution formed, including meso forms and counting enantiomers separately, how many stereoisomers does the diol have? Give the answer as an integer.

Answer: 3

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