Stimulants Why does meth cooked from racemic pseudoephedrine produce primarily d-meth?

[goosestepping]

Hey guys, I am new here and I have found some information and it says that Sudafed (pseudoephedrine hcl) is racemic. Now I am just wondering because I found other information which says that methamphetamine produced by the pseudoephedrine method is mainly dextro and barely any levo, say 80/20, respectively. Now what I cannot make sense of is why this method does not produce racemic methamphetamine? I have noticed that the P2P method will produce equal racemic 50/50 dextro and levo meth, which makes sense. But why does the pseudoephedrine method produce more of one of the enantiomers (the dextro) if the precursor is racemic?

Thank you.

 

[S.J.B.]

Pseudoephedrine, at least that used in medications, is produced by way of an enzymatic process and is essentially enantiopure (>99:1). The methamphetamine derived from it will also be enantiopure.