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The fundamental rules of D/L notation, as I understand it, are as follows;

  • In D/L notation, a molecule is named by mapping it to glyceraldehyde.
  • The D/L notation is based on the stereo configuration of d-glyceraldehyde, and compounds that can be made without disrupting this stereo configuration are designated as D-forms, and their mirror-isomers are designated as L-forms. Here, the distinction between whether the reference substance, d-glyceraldehyde, is a d-body (d is lowercase-letter) or an l-body can be determined experimentally from polarization experiments.

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My questions:

  • But can "without disrupting this stereo configuration" in the abovementioned be done under a uniform rule?
  • If there is such a uniform rule, what exactly is it?
  • Why is S-3 hydroxyacyl-CoA, for example, L-body?
  • As another example, for what reason was the L-body of thalidomide treated as an L-body?

As a "local rules" applicable only to amino acids, there seems to be a known method of distinguishing between D and L bodies in the following manners. (In practice, perhaps only alpha amino acids can be distinguished?)

'Local rules' for amino acids;

  • (1)H for H
  • (2)OH for NH2
  • (3)COOH for CHO
  • (4)R for CH2OH

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But then, why is S-3 hydroxyacyl-CoA an L-body?

Although a simple mapping of β-hydroxyacyl-CoA to glyceraldehyde would be as follows;

  • (1)Corresponding H to H
  • (2)OH to OH
  • (3)CH2CO-S-CoA to CHO
  • (4)R for CH2OH

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But, the above method of mapping different atomic groups seems quite arbitrary. Why do you map them in this way? Is there any logic that justifies such a correspondence?

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