摘要:
The optical isomers of racemic 1,2-diols are separated by enzymatic way, byeans of a process involving the following operations:reaction of the racemic mixture of the 1,2 diols with an organic anhydride in the presence of enzyme belonging to the class of lipases;separation of the enzyme;removal of the excess of anhydride;separation of the produced esters, in optically pure form by column chromatography;recovery of the 1,2 diols, as optically pure enantiomers.
摘要:
A process is described for separating the optical isomers of 1,2-isopropylideneglycerol, of formula (I), comprising partially stereoselective enzymatic hydrolysis of 1,2-isopropylideneglycerol benzoyl ester (II) catalyzed by a free or immobilized lipase, the hydrolysis being conducted in the presence of a cosolvent and followed by crystallization enabling crystals of (II) in raceme form and mother liquor containing (II) in the form of the pure enantiomer to be selectively obtained.The compound (I) is widely used industrially as an intermediate in the synthesis of chiral drugs such as (R)-(-)-carnitine, (S)-beta-blockers, (S)-antiviral agents, analgesic drugs etc.
摘要:
A process is described for the separation of the optical isomers of alphayl- or alpha-aryloxy- carboxylic acids by means of the stereoselective hydrolysis of racemic alkyl esters of the above acids in the presence of bacteria or their enzymes, selected from the species Brevibacterium, Bacteridium, Micrococcus, and Bacillus.
摘要:
The biotechnological resolution by means of stereoselective enzymatic thio-transesterification of the racemic mixture of the optical isomers of the compounds of formula (I): ##STR1## wherein: R, R' and R", alike or different form one another, represent a linear alkyl group of from C.sub.1 to C.sub.4, in the presence of an alcohol and an enzyme capable of selectively causing the reaction of thio-transesterification of the (L)-isomer to take place, with the (D)-isomer remaining substantially unchanged, and being then separated by means of per se known techniques.
摘要:
A process for synthesizing aromatic urethanes, which entails:a) reacting an organic carbonate, in an amount which is equal to or greater than a stoichiometric amount, with an aromatic amine at a temperature of00 to 190.degree. C.; andb) recovering the aromatic urethane from the reaction mixture, wherein step a) is carried out by maintaining reaction alcohol in an amount of from 10 to 40 mol % based on a total quantity of alcohol coproduced during the reaction.
摘要:
A process is described for the preparation of aromatic carbamates in which an organic carbonate in a stoichiometric quantity or in a quantity higher than the stoichiometric value is reacted with an aromatic amine operating in the presence of a carbamation catalyst, wherein this catalyst is selected from N,N-substituted carbamate complexes of zinc or copper. The process gives high yields and selectivity in the useful reaction product.
摘要:
The present invention relates to a process for producing large amounts of 7.beta.-(4-carboxybutanamido)-cephalosporanic acid acylase ("GA") enzyme, which process consists in growing, under suitable culture conditions, a recombinant Escherichia coli K12 strain and subsequently extracting the enzyme from the resulting culture.Enzyme production is controlled by a particular expression system which can be induced by corn-steep liquor, an extremely low cost component of the culture medium.The enzyme can be used in the enzymatic preparation of 7-amino-cephalosporanic acid by starting from 7.beta.-(4-carboxybutanamido)-cephalosporanic acid.
摘要:
Integrated process for the preparation of aromatic isocyanates comprising: the reaction between an aromatic amine and an organiccarbonate in the presence of a catalyst selected from organic and inorganic salts of a metal selected from Zn, Sn, Pb, Cu; the removal of the catalyst; the passivation of the quantity of residual metal in the urethane formed in step a); the removal of the organic solvent and its optional recycling to step a) of the reaction; the evaporation of the aromatic urethane with partial pyrolysis; the complete pyrolysis of the urethane in gas phase; the recovery of the isocyanate.
摘要:
The present invention relates to a process for producing large amounts of 7.beta.-(4-carboxybutanamido)-cephalosporanic acid acylase ("GA") enzyme, which process consists in growing, under suitable culture conditions, a recombinant Escherichia coli K12 strain and subsequently extracting the enzyme from the resulting culture. Enzyme production is controlled by a particular expression system which can be induced by corn-steep liquor, an extremely low cost component of the culture medium. The enzyme can be used in the enzymatic preparation of 7-amino-cephalosporanic acid by starting from 7.beta.-(4-carboxybutanamido)-cephalosporanic acid.
摘要:
A process is described for the preparation of aromatic urethanes in which organic carbonate in a stoichiometric quantity or in a quantity higher than the stoichiometric value is reacted with an aromatic amine operating in the presence of a carbamation catalyst, wherein this catalyst is selected from zinc and/or copper carbonate hydroxide. The process gives high yields and selectivity in the useful reaction product.