150323-35-6Relevant articles and documents
Process for preparing 2-piperazinecarboxylic acid derivatives
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, (2008/06/13)
A process for preparing 2-piperazinecarboxamides in the form of their enantiomers or their enantiomer mixtures of the general formula: STR1 wherein R1 is (a) unsubstituted or substituted alkyl or (b) --OR4, wherein R4 is unsubstituted or substituted alkyl, alkenyl or aryl, or (c) --NR5 R6, wherein R5 is hydrogen or alkyl and R6 is alkyl, and R2 and R3 are identical or different and are hydrogen, unsubstituted or substituted alkyl, alkenyl or aryl, or the radical of an amino acid or an amino acid ester. A 2-piperazinecarboxylic acid of the formula: STR2 or a salt thereof, is first converted into an N-acyl derivative of the general formula: STR3 where R1 and R4 are as defined above. This compound is then cyclized in a second stage in the presence of a halogenating agent to form a piperazinecarboxylic anhydride of the general formula: STR4 where R1 is as defined above, which is finally reacted with an amine of the general formula: STR5 where R2 and R3 are as defined above, to give the end product of the general formula I. Certain piperazinecarboxylic anhydrides are also novel.
Process for preparing optically active piperazine derivatives and Intermediates for preparation
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, (2008/06/13)
Process for preparing optically active 2-piperazine-carboxylic acid derivatives, particularly S-enantiomer thereof, in high yield and high optical purity on industrial scale. As the optical resolving agents, easily accessible sulfonamides derived from selected optically active amino acids, such as N-tosyl-L-phenylalanine, N-tosyl-D-phenylglycine, N-tosyl-L-alanine or N-tosyl-L-valine, give excellent results. These resolving agents are stable and easily recovered from the reaction mixture and reused. Resolved 2-piperazinecarboxylic acid derivatives are preferably isolated as 4-t-butoxycarbonyl (Boc) derivatives. Diastereomeric salts (an example being shown below) formed as the intermediates of resolution are novel. STR1 ?In the formula "Ar" stands for a phenyl or naphthyl group which may be substituted with one to three C1-C6 alkyl groups, halogen atoms, nitro or alkoxy groups; and n=0 or 1.!
Asymmetric hydrogenation of tetrahydropyrazines: Synthesis of (S)-piperazine-2-tert-butylcarboxamide, an intermediate in the preparation of the HIV protease inhibitor indinavir
Rossen,Weissman, Steven A.,Sager,Reamer,Askin,Volante,Reider
, p. 6419 - 6422 (2007/10/02)
Hydrogenation of tetrahydropyrazine 4g with [(R)-BINAP(COD)Rh]TfO gave piperazine 6g in 96% yield and 99% ee. Simple hydrogenolytic deprotection and crystallization afforded the key chiral (S)-N-Boc-piperazine MK-639 intermediate I in high yield and enant