Esterification Weigh 147g of L-glutamic acid, put it into a three-neck bottle, add 1L of absolute ethanol, stir and cool to 0°C, then add 480ml of H2SO dropwise, stir and react at 0-5°C for 1h, continue to react at room temperature for 1h, and the reaction is complete become clear. Add triethylamine dropwise at 20°C until the pH is 8-8.5, white crystals precipitate out, stir at room temperature for 1 hour, let stand and cool at 5°C and filter, take the crystals, wash with 95% ethanol, vacuum dry after vacuuming to obtain Glutamic acid-δ-ethyl ester is about 141g. The melting point is 178-180°C, and the yield is 80%-83%. [α]32D+29.8 (C=1g/ml10%HCl).
Reduction Put 175g of glutamic acid-δ-ethyl ester into a three-neck flask, add 875ml of distilled water, stir and cool to 5°C, then add KBH453.9g in portions for about 1h, then react at room temperature for 1h, keep warm at 50°C for 3h . Cool to 0°C, add 6mol/L HCl to adjust the pH to 4, and filter to get the filtrate to obtain the crude L-proline aqueous solution.
Ion exchange resin-alumina column chromatographic separation put the crude L-proline aqueous solution into the 732-H+ type resin exchange column at a flow rate of 4ml/min (10ml resin is required for 1g acid feeding). Rinse with distilled water until neutral, then elute with 1mol/L ammonia water, and collect the eluate containing the L-proline segment (controlled by silica gel G thin-layer chromatography). Concentrate the eluate to dryness under reduced pressure, dissolve it with a small amount of water, put it into a neutral alumina chromatographic column, and then elute it with 60% ethanol aqueous solution (still controlled by silica gel G thin-layer chromatography). The collected eluate was concentrated to dryness under reduced pressure, washed several times with absolute ethanol, cooled slightly, then added with anhydrous ether, cooled and filtered to obtain crystals, dried in vacuum to obtain L-proline. The melting point is 220-222°C (decomposition), and the yield is about 28%. [α] 24D-82.4 (C=1g/ml, H2O).
For salt formation, put the crude proline aqueous solution in a reaction flask, add pentachlorophenethanol solution (0.111mol/70ml ethanol) dropwise when heated to 50°C, keep stirring for 5 hours, let cool to 0°C, and filter to collect crystals , washed with a small amount of ice water, drained, and dried to obtain a double salt with a melting point of 240-242°C and a precipitation rate of 95%.
Analysis Put 38.4g of double salt into a three-neck bottle, add 200ml of distilled water, 20ml of ammonia water, stir at room temperature for 8h, cool to 0°C, filter and take the filtrate, concentrate the filtrate under reduced pressure, add 100ml of distilled water, filter and take the filtrate, add activated carbon for decolorization . Extract with ether, separate the water layer, continue to concentrate to dryness, decolorize with absolute ethanol several times, add a small amount of absolute ethanol to moisten, add 2 times the amount of anhydrous ether, cool and crystallize, filter to obtain crystals, and vacuum dry to obtain L-preserved Amino acid finished product.
Esterification Put 15kg of L-glutamic acid and 100L of absolute ethanol into a 200L reaction tank, cool to 0°C, add 48.1L of concentrated H2SO4 dropwise under stirring conditions, keep at 0°C, stir for 1h, then keep warm at 25°C for 1h Afterwards, triethylamine was added to make the pH 8.0-8.5. After stirring for 1h, a white precipitate appeared. Cool to 5°C, filter the precipitate, wash with 50L of 95% ethanol, and dry the precipitate in vacuum at 50°C to obtain L-glutamic acid-δ-ethyl ester.
Reduction Put the obtained L-glutamic acid-δ-ethyl ester into a 100L reaction tank, add 70L of water, stir and cool to 5°C, add 4.3kgKBH4 in portions within 1h, heat and keep at 200°C, stir for 1h, and then raise the temperature for 50°C °C, stirred for 3-4h, cooled to 0 °C, adjusted the pH to 4.0 with 6mol/L HCl, filtered the filtrate to obtain a crude L-proline solution.
Precipitation Put the L-proline crude product solution into a 100L reaction tank, heat to 50°C, slowly add 7L of 1.5mol/L pentachlorophenol ethanol solution under constant stirring, keep warm at 50°C for 5 hours, then cool to 0°C Crystals were precipitated, and the crystals were collected by filtration, and dried to obtain double salts.
Analysis and purification Put the double salt into a 100L reaction tank, add 20L of 3% ammonia water, stir and react at room temperature for 7-8 hours, cool down to 0°C and filter, wash the precipitate with a small amount of ice water, drain, combine the washing liquid and filtrate, and then reduce Concentrate under pressure to dryness, stir and dissolve with 10L deionized water, filter the filtrate, add 0.5% activated carbon, heat at 70°C and stir for decolorization for 1h, filter the filtrate, let it cool to 0°C, add an equal volume of ether for extraction, and separate the water layer , concentrated to dryness under reduced pressure, added 10L absolute ethanol to dehydrate 3 times, drained, added 2L absolute ethanol to the precipitate, stirred evenly, then added 10L ether, cooled to 0°C, filtered to collect the precipitate, vacuumed ether, and dried at 80°C , in L-proline finished product.