[dielsalder33]

Hi,

in the last days I became interested in very reliable methods for the enantioselective synthesis of alpha amino acids (also D-amino acids) using some kind of alkylation step (different Alkyl-Br are quite easy to make) in alpha position.

I have too main questions:

1) What is the best (=fastest) method in a research lab?
2.) How is it done in industy?

I have not found so many great methods which are really practical, universal and also enable the enantioselective synthesis of D-amino acids. So far, methods employing chiral phase transfer catalysts seem to be very good but expensive. I also know of the classic Schöllkopf method, but this one is not applied in larger scale.
I remember the groundbreaking synthesis of L-DOPA by Knowles, but is there an easy access to the modified starting materials by some metal organic reaction using Alkyl-Br?

Thank you for your experiences and ideas!

[AWK]

Tetrahedron Letters
Volume 38, Issue 49, 8 December 1997, Pages 8595-8598

http://pubs.acs.org/doi/abs/10.1021/ja991062w

[movies]

The most cost-effective industrial methods are certainly hydrogenations like the Knowles method and the like.  It comes down to recyclability of the catalysts, incredibly low catalyst loadings, and the fact that H₂ is very cheap.  Note that there are some significant limitations, however.

In the lab, I think the Schollkopf system is fantastic.  There are also means with an Evans auxiliary, but they aren't quite as nice.  You can also make amino alcohols by means of the Ellman auxiliary, which is also pretty convenient.