China 
Africa 
Explore chapters and articles related to this topic
Laccase-Mediated Synthesis of Novel Antibiotics and Amino Acid Derivatives
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2019
The aromatic amino group of 4-aminobenzoic acid has decreased basicity because the lone pair of electrons from the nitrogen is delocalized into the ring and could not be used for protonation. In contrast, aliphatic amino groups like the amino group of the amino-ß-lactams have elevated basicity; they are protonated and have to be deprotonated for the amination by Michael addition. The highly reactive quinoid intermediates of 3,4-dihydroxybenzoic acid (64), 3,4-dihydroxyphenylacetic acid (65) and 3-(3,4-dihydroxyphenyl)-propionic acid (66) react to a variety of inseparable homomolecular dimers or oligomers or products formed by abiotic follow-up reactions in addition to the slower formation of heteromolecular dimers (Fig. 8.4).
Impacts of hydrotropes on clouding phenomena and physico-chemical parameters coupled with the triton X 100 & promethazine hydrochloride mixture
Published in Molecular Physics, 2023
S. M. Rafiul Islam, Md. Rafikul Islam, Shamim Mahbub, Kamrul Hasan, Dileep Kumar, Javed Masood Khan, Anis Ahmad, Md. Anamul Hoque, D. M. Shafiqul Islam
The phase separation performance of the surfactant-drug mixture is unique properties and may change in the presence of foreign solutes like different salts and HDTs. Generally, the solubility of any regular substances increases with the enhancement of temperatures. However, the reverse result is observed for the NIS solution. The heating of NIS in aqueous solvent media destroys the H-bonding between surfactant and water hence the solubility of surfactant decreases. The formation of a sizeable hydrophobic network in aqueous media, which results in insolubility and corresponding phase separation occurs [49]. The CP phenomenon for NIS-drug mixture in the presence or absence of additives is crucial because phase separation of NIS-drug mixture is energetically controlled. We investigated the changes of CP of TX 100 + PMH in different concentrations of HDTs in aqueous media. From the literature, it is known that the micellization of TX 100 takes place at TX-100 concentration in the range of 0.20–0.31 mM, the result obtained from surface tension method at 298 K [50]. Consequently, we have selected much higher concentration of TX 100 (25 mmol kg−1) in the present examination so that all the surfactant molecules remain as the micellized form. The concentration of PMH in the current investigation was 1.0 mmol kg−1. The PMH drug undergoes micellization at 38.31 mmol kg−1 concentration of PMH at 298.15 K [51]. Therefore, PMH is probable to occur in the monomeric form in the present investigating system. The CP values are obtained to be changed with the alteration of HDTs concentrations, which suggests that the CPs are dependent on the concentrations of HDTs. Table 2 summarises the consequences of hydrotropes on the cloudy development of the experimental system. The CP values for TX 100 + PMH drug mixture enhanced with increasing concentration of HDTs in aqueous media except aq. 4-aminobenzoic acid (4-AmB). The CP values for the mixture of TX 100 + PMH containing different HDTs (at nearly 100 mmol kg−1) in water follow the order with respect to different HDTs: .