According to the figure below, reacting 2,6-dimethylaniline with the acid chloride of pyri-dine-carboxylic acid first gives the 2,6-xylidide of a-picolinic acid (2.2.4). Then the aromatic pyridine ring is reduced to piperidine by hydrogen in the presence of a platinum on carbon catalyst.
The resulting 2,6-xylidide a-pipecolinic acid (2.2.5) is methylated to mepivacaine using formaldehyde with simultaneous reduction by hydrogen in the presence of platinum on carbon catalyst .
Mepivacaine is similar to lidocaine in terms of properties; however, it has longer lasting effects. Synonyms of mepivacaine are carbocaine and estradurin.
Bupivacaine: Bupivacaine, N-2,6-(dimethyl)1-butyl-2-piperidincarboxamide (2.2.7), is chemically similar to mepivacaine and only differs in the replacement of the N-methyl substituent on the piperidine ring with an N-butyl substituent. There are also two suggested methods of synthesis. The first comes from a-picolin-2,6-xylidide (2.2.4). The alkylation of the last with butyl bromide gives the corresponding pyridine salt (2.2.6). Finally, it is reduced by hydrogen using platinum oxide as a catalyst into a piperidine derivative—bupivacaine [13,16].
The other method results directly from the piperidine-2-carboxylic acid chloride, which is reacted with 2,6-dimethylaniline. The resulting amide (2.2.8) is further alkylated with butyl bromide to bupivacaine [17-19].
Like lidocaine and mepivacaine, bupivacaine is used in infiltration, spinal, and epidural anesthesia in blocking nerve transmission. Its most distinctive property is its long-lasting action. It is used for surgical intervention in urology and in lower thoracic surgery from 3 to 5 h in length, and in abdominal surgery lasting from 45 to 60 min. It is used to block the trifacial nerve, the sacral and brachial plexuses, in resetting dislocations, in epidural anesthesia, and during Cesarian sections. The most common synonym for bupivacaine is marcaine.
Ethidocaine: Ethidocaine, N-(2,6-dimethylphenyl)-2-(ethylpropylamino)butanamide (2.2.12), is also an anilide of a-dialkylaminoacid; however, the sequence of reactions for its formation differs somewhat from those examined above. In the first stage of synthesis, 2,6-dimethylaniline is reacted with a-bromobutyric acid chloride to give the bromoanilide (2.2.9). Next, in order to increase the yield of the final product a substitution of bromine atom for an iodine atom had been done. The resulting iodine derivative (2.2.10) easily reacts with propylamine, forming aminoamide (2.2.11), which undergoes further N-ethyl-ation using diethylsulfate to give ethidocaine [20,21].
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