Patent US3658831A successfully refreshed from Google Patents.
US3658831A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for the preparation of n-carboxylic acid anhydrides of glutamic acid-gamma-esters
Assignee: KH Neochem Co Ltd
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Filing: 1969-01-07
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Granted: 1972-04-25
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Expires: 1989-01-07
Abstract
Abstract A PROCESS FOR THE PREPARATION OF N-CARBOXYLIC ACID ANHYDRIDES OF GLUTAMIC ACID-$ESTERS WHICH COMPRISES SUSPENDING A GLUTAMIC ACID-$-ESTER IN ASOLVENT MIXTURE OF AN AROMATIC HYDROCARBON, FOR EXAMPLE, BENZENE, TOLUENE OR XYLENE, AND AN ORGANIC NITRILE, FOR EXAMPLE, ACETONITRILE PROPIONITRILE OR ACRYLONITRILE, AND REACTING THE SAME WITH PHOSGENE. PREFERABLY, ABOUT 40% OR LESS BY VOLUME OF THE NITRILE IS EMPLOYED. THE PROCESS PROVIDES PRODUCTS SUBSTANTIALLY FREE OF HALOGEN IMPURITIES, WHICH PRODUCTS CAN BE POLYMERIZED TO POLYGLUTAMIC ACID-$-ESTERS.
Inventors
- 👤 Yasuo Fujimoto
- 👤 Keizo Tatsukawa
- 👤 Masayuki Teranishi
- 👤 Yoichi Koiwa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 17:00
CPC Classifications
C; C07; C07D; C07D263/00; C07D263/02; C07D263/30; C07D263/34; C07D263/44
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-04-25 | 1975-10-25 | 1976-04-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-04-25 | 1979-10-25 | 1980-04-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-04-25 | 1983-10-25 | 1984-04-25 | $7700.00 | Window Closed / Lapsed |