Presence Of Thiophenol Research Articles

Human proinsulin, VIII: studies on the S-tritylation of reduced proinsulin, insulin A and B chains and their detritylation.

Reduced proinsulin and insulin A and B chains were selectively and quantitatively converted to hexa(S-trityl)proinsulin, tetra(S-trityl)A chain and di(S-trityl)B chain. These derivatives were used as models to investigate the quantitative removal of S-trityl groups. Amongst the various detritylation methods studied, the best procedure was found to be acidolytic cleavage with trifluoroacetic acid in the presence of thiophenol or benzylmercaptan as cation scavengers. The detritylated derivatives, upon oxidative sulphitolysis, yielded electrophoretically homogeneous hexa(S-sulphonate)proinsulin, tetra(S-sulphonate)A chain and di(S-sulphonate)B chain. The hexa(S-sulphonate)proinsulin was reduced and reoxidized to proinsulin.

Studies of methyl methacrylate–glycidyl methacrylate copolymers: Copolymerization to low molecular weights and modification by ring‐opening reaction of epoxy side groups

AbstractThe copolymerization of methyl methacrylate (MMA) with glycidyl methacrylate (GMA) at 60°C with 2,2′‐azobisisobutyronitrile (AIBN) as radical initiator and in the presence of thiophenol (TP) as chain‐transfer agent has been investigated. Monomer reactivity ratios for MMA and GMA are found to be r1 (MMA) = 0.80 ± 0.015 and r2 (GMA) = 0.70 ± 0.015, from which Q and e values are calculated to be 0.68 and −0.36 for GMA. The initial rate of copolymerization Rp at 60°C with AIBN (0.02 mole/l.) and TP (0.1, 0.01 mole/l.) were found to increase nonlinearly with increasing GMA concentration in the monomer feed. Homopolymerizations of MMA and GMA monomers were studied in the presence and in the absence of thiophenol. The values of δ (= kt1/2/kp) for MMA and GMA were determined to be 10.25 and 3.00 (mole‐sec/l.)1/2, respectively. Using the values r1 (MMA), r2 (GMA), δ1 (MMA), δ2 (GMA), and Rp, the cross‐termination constants ϕ for MMA–GMA monomers were determined (average value ϕ = 0.42). The increase in Rp values with increasing GMA content has been attributed to the cross‐termination of MMA–GMA radicals. The transfer constant of TP has also been determined for GMA and found to be 1.00. A MMA–GMA copolymer of low molecular weight, containing 2.01% of oxirane oxygen, was modified by opening of the oxirane ring of GMA by reaction with diethanolamine (DEA). The reaction was carried out at 70 ± 1°C, the copolymer content of epoxy groups and the amine being assumed to be in the molar ratio of 1:4. Addition of a hydrogen‐bond acceptor like nitrobenzene decreases, while addition of a hydrogen‐bond donor like phenol increases the rate of epoxy ring opening with DEA. This indicates that a hydrogen‐bonded intermediate is involved in this reaction and that it weakens the epoxy ring and enhances the rate of its opening with DEA. From the studies of the conversion rates, existence of a “nonspecific” side reaction has been shown which involves the reaction of the terminal epoxy groups of the copolymer and the hydroxyl groups of DEA or formed in the reaction with DEA (involves a chain coupling). DEA can be trifunctional in this reaction. This has been further confirmed from the increase of number‐average molecular weights M̄n of the copolymers resulting from this coupling and the nitrogen content in the copolymers after modification with DEA.

Synthesis and biological activity of sulfur containing derivatives of chalcone. II. The reaction of chalcone oxides with thiols

The reaction of chalcone oxide (I) with arylthiol in the presence of triethylamine, or with alkylthiol in the presence of sodium ethoxide, progressed easily to afford aryl or alkyl phenacyl sulfide and benzaldehyde. Similarly 4'-substituted (OCH3, CH3, Cl, NO2) chalcone oxides (II, III, IV, V) reacted with thiophenol in the presence of triethylamine to give the corresponding phenyl 4-substituted phenacyl sulfide and benzaldehyde. 4-Substituted (OCH3, CH3, Cl, NO2) chalcone oxide (VI, VII, VIII, IX) reacted with thiophenol under the same condition to afford phenyl phenacyl sulfide and the corresponding aromatic aldehyde, while, in the case of VIII or IX, additional to give 1-aryl-1-hydroxy 2-phenylthio-3-phenyl-3-propanone (X or XII) as an adduct. The adduct (X or XII) underwent gradual breakdown to phenyl phenacyl sulfide and aromatic aldehyde (p-Cl, p-NO2) in the presence of thiophenol and triethylamine. This fact indicates that an intermediate like X or XII is first formed by the addition of thiols to chalcone oxides and then the intermediate breaks down to the above two components.

Mechanistic studies in strongly basic media. Part VII. Mechanism of the base-induced reaction of 9-bromofluorenes in t-butyl alcohol containing thiophenol

The rate of conversion of 2,9-dibromofluorene into 2,2′-dibromobifluorenylidene by excess of potassium t-butoxide in t-butyl alcohol is markedly reduced in the presence of thiophenol or of 9-fluorenyl phenyl sulphides. It is shown that this effect is related to the ability of the sulphur-containing additives rapidly to convert the halogenofluorene into the related 9,9′-bifluorenyl-9-yl phenyl sulphide which undergoes β-elimination of thiophenol in the rate determining steps of the reaction.