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a-Methyl-Phenylalanine

Started by Lucid_Dreamer, December 07, 2003, 04:56:00 PM

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Lucid_Dreamer

I have been searching all day, I am trying to find synthesis of alpha-methyl-phenylalanine. Rhodium suggested the use of benzaldehyde and provided the link a while back, although the link is now broken...

J. Med. Chem. 14(11), 1132-1133 (1971)
pharmacist.the-hive.tripod.com/alal-amphet.pdf

Rhodium also said there was a way from phenylalanine that involved PTC(phase transfer) but that proved untested and hard to find in the search engines at the sites upon sites.

I did however find an article describing the use of a-methylphenylalanine as a diet supplement, it showed a study in rats, I can provide a link if interested (the link isn't too compelling)

Can someone post the article from the J. Med. Chem.? I have been searching all day, the good side is I can now type phenylalanine as a reflex.


lugh

Here it is:

J. Med. Chem. 14(11), 1132-1133 (1971)

https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000475296-alal-amphet.pdf" target="_blank" title="Download this file">



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Lucid_Dreamer

A practical asymmetric synthesis of a-methyl a-amino acids using a chiral Cu–salen complex as a PTC

DOI:

10.1016/S0040-4039(00)01247-8



Abstract
The asymmetric C-alkylation of N-benzylidene alanine methyl ester has been achieved using a copper(II) (salen) complex as an asymmetric phase transfer catalyst and provides a practical synthesis of a-methyl a-amino acids with up to 86% enantiomeric excess.

Tetrahedron Letters
Volume 41, Issue 37 , September 2000, Pages 7245-7248


Other PTC Reactions

DOI:

10.1016/S0957-4166(99)00185-8



Abstrct
Enantiopure 2-hydroxy-2'-amino-1,1'-binaphthyl (NOBIN) is shown to catalyse C-alkylation of aldimine Schiff's bases of alanine ester under phase-transfer catalysis conditions (solid NaOH or NaH, toluene, ambient temperature, 10% NOBIN). Using (R)-NOBIN, the final (S)-a-methylphenylalanine was obtained in up to 68% ee.

DOI:

10.1016/S0957-4166(98)00044-5



Abstrct
Compound (4R,5R)- or (4S,5S)-2,2-dimethyl-a,a,a',a'-tetraphenyl-1,3-dioxolane-4,5-dimethanol (TADDOL) was shown to catalyze C-alkylation of aldimine Schiff's bases of alanine esters under phase-transfer catalysis conditions (solid NaOH, toluene, ambient temperature, 10% TADDOL) with the e.e. of the final a-methylphenylalanine or a-allylalanine reaching 82%.

DOI:

10.1016/S0040-4039(99)01836-5



Abstract
Application of N-anthracenylmethyl dihydrocinchonidinium bromide as a catalyst for the enantioselective alkylation of a series of alanine-derived imines is reported. Using solid K2CO3/KOH as the stochiometric base such alkylations can be achieved with enantiomeric excesses up to 87% allowing rapid access to a,a-dialkyl-a-amino acid esters.


I am mainly interested in the Copper salen reaction, but the other PTC's wouldn't bother me if they weren't so exotic. Can someone explain to me chiral Cu-Salen complexes? There was another interesting one that I couldn't access the abstract to, titled........ "Asymmetric PTC C-Alkylation Catalyzed by Chiral Derivatives of Tartaric Acid and Aminophenols" found on Beilstein, J.Org.Chem. , Jan 2000.


algebra

Anybee who has seen the article or who might be able to speculate - would formaldehyde be a suitable candidate to form the imine (aldimine) - its the obvious choice since this would lead to the desirable n-methyl structure following decarboxylation),

fucking great refs... - very interesting, well done LucidD.

Lucid_Dreamer

Well, apparently, the alkylation can also be acheived by treating the ester with a methyl halide; methyl chloride, methyl iodide, methyl bromide. Methyl iodide seems to be the most carcinogenic, and also uses RP and I2 for manufacture but I also seen that it can be done with KI maybe? While searching for chloromethane I received mainly DCM stuff. Methyl bromide, or bromomethane is used as a soil fumigant, and should be easy to acquire. Can someone clue me in on whether the methyl halides really work, or if there is an easy way to make any of them?


Aurelius

yes, KI can be used for the synthesis of MeI.  It's one of the rxns referenes in Org. Synth. Coll. Vol.  under the synthesis of MeI.


Lucid_Dreamer

Thanks, It can be made from MeSO4 and KI, and supposedly can be made from methanol and KI. Interestingly enough, chloromethane can be made from methanol and Hcl, I am not sure of all this though, does anyone know if the mrthyl halides work for what I have in mind?


algebra

Just to clarify my stupidity, I am a bit confused which of the following (if any) is N-benzylidene alanine methyl ester.

either -
(1) Bz-CH=N-CH(C)-CO2Me     or...
(2) Bz-CH2-N=C(C)-CO2Me

hoping its the first one - therfore giving the route from phenylalanine, by forming the ester, then the imine, alkalation, decarboxyation

WizardX

(1) Bz-CH=N-CH(C)-CO2Me

Bz-CHO + H2N-C ==> Bz-CH=N-C + H2O

java

Lucid_ Dreamer  did you ever get the article ....


A practical asymmetric synthesis of a-methyl a-amino acids using a chiral Cu–salen complex as a PTC

DOI:10.1016/S0040-4039(00)01247-8

Abstract
The asymmetric C-alkylation of N-benzylidene alanine methyl ester has been achieved using a copper(II) (salen) complex as an asymmetric phase transfer catalyst and provides a practical synthesis of a-methyl a-amino acids with up to 86% enantiomeric excess.

Tetrahedron Letters
Volume 41, Issue 37 , September 2000, Pages 7245-7248


also did you have any success in alkylating the alpha carbon of Phenylalanine, followed by decarboxylation to amph?.......java


amalgum

Why don't you just buy alpha-methyl-phenylalanine?  A quick google search turns up hundreds of suppliers.  It isn't watched or suspicious.