Suggest how you might attempt a synthesis of an optically active sample of eithe

Question

Suggest how you might attempt a synthesis of an optically active sample of either 2- or 2-hydroxy-trans-10-methyl-decalin starting from (+/-)-trans-1-methylbicyclo[4.4.0]dec-3-ene (structure below). How could you prove the relative configuration of the sample which you have prepared? (How can you prove that it is and not or vice-versa?) How could you determine the absolute configuration of the sample you have prepared? (X-ray crystallography may not be utilized and you are to assume that the data [physical properties] normally found in the library are not available.)

Explanation / Answer

Racemic mixtures can be separated, or resolved, into their pure enantiomers by three methods. The first method is to mechanically separate the crystals in such a mixture based on differences in their shapes. This was the method first used by Pasteur, and it is mainly of historical interest.

The second resolution method employs enzymes. Enzymes are stereospecific chiral protein molecules that act as catalysts. Because of their chirality, these molecules react with only one enantiomer in a racemic mixture. The enantiomer that momentarily bonds to an enzyme undergoes reaction, while the enantiomer that does not bond remains unchanged. The unreacted enantiomer can then be removed from the reaction mix by ordinary separation methods, such as distillation or recrystallization.

The third method involves converting the enantiomers of a racemic mixture into diastereomers and then resolving that mixture with ordinary separation techniques. The separated diastereomers are then treated with appropriate reagents to regenerate the original enantiomers.

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