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Author: Subject: phenylalanine -> amphetamine
suddenmulch
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[*] posted on 10-11-2010 at 05:14
phenylalanine -> amphetamine


there was a rather complicated synthesis here and i knocked together one that i thought might be similar, but knowing me probably won't work. some feedback would be good.

first, like rhodium, reduce the carboxyl with LiBH4 to a hydroxyl. but then instead dehydrate that (conc. H2SO4 or something) to get a double bond, then hydrogenate that to get your methyl group and voila! cheers.
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[*] posted on 10-11-2010 at 06:12


No it won't work, the reason they go through all that complicated folderol is to protect the amino group and the chiral centre during their conversion of a carboxyl group to a methyl group.
Your reaction scheme will result in black goo when you try to dehydrate the amino alcohol, double bonds do not like sitting next to amino groups! :(
Another point is that D phenylalanine does not occur naturally so it has to be made and is consequently very expensive.
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suddenmulch
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[*] posted on 10-11-2010 at 07:38


bollocks, i thought the dehydration step would be where it would fall apart. :(

but going to the point about d-Phe, surely making L-amphetamine isn't a complete disaster if you used the original synthesis? it's not that mild!

[Edited on 10-11-10 by suddenmulch]
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[*] posted on 10-11-2010 at 10:10


This is basically a 'because we can synthesis', it shows off some very elegant and clever chemistry but it is basically pretty useless.
There are faster, easier and cheaper ways to make amphetamine in higher yields using more readily available reagents.
There are plenty of places in the world where chemicals and indeed some parts of the chemical industry are only lightly or not regulated at all plus some places where the rule of the state has collapsed altogether.
Amphetamine can be made in these places without worrying about busies or flics interfering in your business and this is where most of the world's supply comes from now!
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[*] posted on 10-11-2010 at 10:49


Since expensive watched reagents are not a problem,
there is this antique method for a racemic modification --
Henry reaction followed by hydride reduction.

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[*] posted on 10-11-2010 at 12:20


The dehydration step could possibly be modified using 70% H2SO4 and steam distillation as can be done with ephedrine to yeild Phenyl-2-Propanone as in this link

That seems a little useless since it destroys the chiral center and a reduction of the alcohol using red phosphorus and Iodine seems simpler.
Or conversion to a halide followed with a reduction to the alkane. All this would be more effective then whats posted in that link.




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