262604-05-7Relevant academic research and scientific papers
METHOD OF 4-BORONOPHENYLALANINE PRODUCTION
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Paragraph 0039, (2019/09/12)
The present invention relates to a method of production of 4-boronophenylalanine (BPA) from 4-iodophenylalanine, in which all the functional groups of the amino acid are protected by benzyl protection method, and which uses isopropyl magnesium halogenide stabilized by a complexation base, and subsequent condensation of the resulting Grignard reagent with a boric acid ester. The final reaction step, catalytic hydrogenolysis or transfer hydrogenolysis of protecting groups on the amino acid, occurs after hydrolysis of the boronate ester groups.
A practical method for the synthesis of enantiomerically pure 4-borono- L-phenylalanine
Nakamura, Hiroyuki,Fujiwara, Masaru,Yamamoto, Yoshinori
, p. 231 - 235 (2007/10/03)
Enantiomerically pure L-BPA (4-borono-L-phenylalanine) was synthesized from L-tyrosine or 4-iodo-L-phenylalanine derivatives using the palladium- catalyzed cross-coupling reaction of pinacolborane (2,3-dimethyl-2,3- butanediolatoboron). Cbz-Tyr(Nf)-OBzl (2b) underwent the cross-coupling reaction with pinacolborane (1) in the presence of [PdCl2(PPh3)2] catalyst to give N-benzyloxycarbonyl-4-(2,3-dimethyl-2,3-butanediolatoboryl)-L- phenylalanine benzyl ester (3a) in 58% yield. The reaction of the 4-iodo-L- phenylalanine derivatives, such as N-benzyloxycarbonyl-4-iodo-L-phenylalanine benzyl ester (2c), N,N-dibenzyl-4-iodo-L-phenylalanine benzyl ester (2d), (4S)-3-benzyloxycarbonyl-4-(4-iodobenzyl)-5-oxazolidinone (2e), and (4S)-3-t- butyloxycarbonyl-4-(4-iodobenzyl)-5-oxazolidinone (2f), with 1 proceeded very smoothly in the presence of [PdCl2(dppf)] catalyst, giving N- benzyloxycarbonyl-4-(2,3-dimethyl-2,3-butanediolatoboryl)-L-phenylalanine benzyl ester (3a), N,N-dibenzyl-4-(2,3-dimethyl-2,3-butanediolatoboryl)-L- phenylalanine benzyl ester (3b), (4S)-3-benzyloxycarbonyl-4-[4-(2,3-dimethyl- 2,3-butanediolatoboryl)benzyl]-5-oxazolidinone (3c), and (4S)-3- butyloxycarbonyl-4-[4(2,3-dimethyl-2,3-butanediolatoboryl)benzyl]-5- oxazolidinone (3d), respectively, in high yields. Deprotection of 3a-d gave enantiomerically pure L-BPA in high total yields.
