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Resolution of D,L-dehydroproline
| Details |
Inventors: Felix, Arthur Martin;
Assignee: Hoffmann-La Roche Inc. (Nutley, NJ)
Primary Examiner: Daus; Donald G.
Assistant Examiner: Vaughn; Mary C.
Attorney, Agent or Firm: Welt; Samuel S., Gould; George M.
D,L-3,4-dehydroproline is resolved in high optical yield by conversion to its N-protected derivative, treatment with R(+)alpha-methyl-p-nitrobenzylamine to form the diastereomeric salts, fractional crystallization, decomposition of the L-R salt and regeneration of the secondary amine group. The product L-3,4-dehydroproline obtained in extremely high optical purity is useful as an inhibitor of collagen synthesis. |
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DETAILED DESCRIPTION I claim: 1.
A method for the preparation of L-3,4-dehydroproline comprising in combination the steps of: A.
treating N-protected D,L-3,4-dehydroproline with R(+)-alpha-methyl-p-nitrobenzylamine so as to form the corresponding diastereomeric salt, the said N-protecting group being selected from conventional N-protecting groups which can be deblocked without racemization of the resolved compound; B.
selectively crystallizing the N-protected L-3,4-dehydroproline (R)-alpha-methyl-p-nitrophenethyl ammonium salt from solution; C.
decomposing the aforesaid diastereomeric salt with cold aqueous weak acid so as to produce N-protected-L-3,4-dehydroproline; and D.
removing the N-protecting group under conditions which do not cause racemization thereby yielding L-3,4-dehydroproline.
2.
The process of claim 1 wherein said N-protecting group is selected from t-butyloxycarbonyl, formyl, trifluoroacetyl and phthaloyl.
3.
The process of claim 2 wherein said N-protecting group is t-butyloxycarbonyl and the deblocking is accomplished by treatment of the resolved protected compound with aqueous formic acid.
4.
The process of claim 1 wherein the formation of the diastereomeric salt in step (A) is carried out in lower alkanol or lower alkyl ketone solvent.
5.
The process of claim 4 wherein said solvent is isopropanol.
6.
A method for the preparation of L-3,4-dehydroproline and D-3,4-dehydroproline comprising in combination the steps of: A.
treating N-protected D,L-3,4-dehydroproline with R(+)-alpha-methyl-p-nitrobenzylamine so as to form the corresponding diastereomeric salt, the said N-protecting group being selected from conventional N-protecting groups which can be deblocked without racemization of the resolved compound; B.
selectively crystallizing the N-protected L-3,4-dehydroproline-(R)-alpha-methyl-p-nitrophenethyl-ammonium salt from solution; C.
decomposing the aforesaid diastereomeric salt with cold weak aqueous organic acid so as to produce N-protected L-3,4-dehydroproline; D.
removing the N-protecting group under conditions which do not cause racemization thereby yielding L-3,4-dehydroproline; E
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