Process for preparing the d-threo isomer of methylphenidate hydrochloride
US6162919A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 3, 1998 |
| Grant date | Dec 19, 2000 |
| Priority date | — |
| Expiry date | Dec 3, 2018 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC07D211/34
- WIPO fieldOrganic fine chemistry
- WIPO sectorChemistry
Abstract
A process for preparing the d-threo isomer of methylphenidate hydrochloride comprising converting d,l-threo methylphenidate hydrochloride to the free base form in a first step, resolving the free base prepared in the first step with (R)-(-)-1,1'-binaphthyl-2,2'-diyl hydrogen phosphate to obtain the phosphate salt enriched with the d-threo isomer of methylphenidate in a second step, basifying the phosphate salt to obtain the free base form of the d-threo isomer of methylphenidate in a third step, converting the free base to the hydrochloride salt form of the d-threo isomer of methylphenidate in high optical purity in a fourth step, and recrystallizing the hydrochloride salt form to obtain the desired d-threo isomer in a higher optical purity. An alternative embodiment relates to the preparation of the d-threo isomer of methylphenidate hydrochloride utilizing the hydrochloride salt form of the racemic mixture of threo-methylphenidate directly.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.