Modification of poly(vinyl chloride). X. Crosslinking of poly(vinyl chloride) with a soft segment of an elastomer containing thiol groups

To obtain poly(vinyl chloride) (PVC) of excellent toughness, a new method of crosslinking PVC is proposed in which PVC is crosslinked with the soft segment in an elastomer such as liquid Thiokol. The reaction can be accomplished by immersing PVC–Thiokol blends in liquid ammonia at 20–30°C. A similar reaction occurs in aqueous ammonia when hexamethylphosphoramide is used as an activator. Characteristics of the crosslinked PVC thus obtained and of the controls of a similar uncrosslinked composition (PVC–Thiokol LP-8, 100:5 by weight) were as follows: tensile strength, 7.3 and 4.8 kg/mm²; elongation at break, 30 and 2.5%; Young's modulus, 3.5 × 10⁴ and 2.9 × 10⁴ kg/cm²; tensile impact, 88 and 15 kg-cm/cm³, respectively. The crosslinked PVC as plasticized with dioctyl phthalate (DOP) and the control blend (PVC–Thiokol LP-8–DOP, 100:10:10 by weight), respectively, showed tensile strengths of 5.9 and 4.8 kg/mm², elongations at break of 44 and 24%, Young's moduli of 2.5 × 10⁴ and 1.6 × 10⁴ kg/cm², and tensile impact strengths of 62 and 120 kg-cm/cm³. As the crosslinkage through the soft segments increases up to about 5%, the elongation at break, Young's modulus, and tensile impact, in addition to the tensile strength, are improved. This is different from the results so far observed with the crosslinked amorphous polymers and is characteristic of the products of crosslinking through the soft segment. The experimental results are discussed in this paper.     

Synthesis and absolute configuration of A-factor,the inducer of streptomycin biosynthesis in inactive mutants of Streptomyces griseus

The absolute configuration at C-3 of A-factor, 2-(6-methylheptanoyl)-3-hydroxymethyl-4-butanolide $\text{1a}$, was determined to be $\text{S}$ by synthesizing(3$\text{S}$)-(+)-A-factor.     

Determination of the absolute configuration at C-6 and C-7 of serricornin (4,6-dimethyl-7-hydroxy-3-nonanone), the sex pheromone of the cigarette beetle

The absolute configuration at C-6 and C-7 of serricornin was established as (6$\text{S}$, 7$\text{S}$) by synthesizing its (6$\text{R}$, 7$\text{S}$-$\text{erythro}$ and (6$\text{R}$, 7$\text{R}$-$\text{threo}$ isomers.     

New water-soluble host molecules derived from calix[6]arene

4-Sulfonate derivatives of calix[6]arene and O-n-hexylcalix[6]arene (1a and 1b, respectively) were synthesized. Measurements using fluorescence and absorption spectral probes indicated that the cavity of calix-[6]arene can accept a naphthalene molecule but not a pyrene molecule and that (1b) has a hydrophobic cavity constructed from the aggregate of the hexyl groups while (1a) provides a reaction field apparently more polar than water. This is the first example for water-soluble host molecules derived from calix[6]arene.     

Synthesis of the enantiomers of 5-hexadecanolide,the pheromone of the queen of the oriental hornet,vespa orientalis,employing enzymic resolution of (±)-2-aminotridecanoic acid as the key-step

Optical resolution of(±)-2-chloroacetylaminotridecanoic acid with amino acylase gave (S)-2-aminotridecanoic add, which was converted into highly optically pure (S)-5-hexadecanolide (the pheromone of Vespa orientalls). Similarly (R)-2-chloroacetylammotridecanoic acid recovered after the enzymic hydrolysis yielded (R)-5-hexadecanolide. The existing methods for the preparation of the enantiomers of 5-hexadecanolide were critically surveyed to point out basic requisites for an effective chiral synthesis.     

Synthesis of the highly potent prostanoid FP receptor agonist, AFP-168: a novel 15-deoxy-15,15-difluoroprostaglandin F2α derivative

A novel 15-deoxy-15,15-difluoro-prostaglandin(PG)F_2α derivative 6 (AFP-168) has been synthesized from the Corey aldehyde in six steps. A key aspect of this route is difluorination of an enone and a stereoselective Wittig reaction. The compound shows high affinity to the FP receptor and potent activities for an anti-glaucoma agent.     

Rapid measurement of oestradiol and oestriol by high-performance liquid chromatography after automatic pretreatment

A fluorometric liquid chromatographic method was developed for measurements of unconjugated oestradiol and oestriol in the serum of pregnant women. The serum samples are injected directly into the apparatus and pass to a pretreatment column, where oestrogens are adsorbed while hydrophilic components such as proteins and carbohydrates are not. The oestrogens then pass into a separation column containing a new type of polymer gel. The mobile phase consists of an acetonitrile-water mixture, and separation is achieved by a reversed-phase mechanism. The eluent is monitored for fluorescence. Data on the reproducibility and recovery by this method and the correlation of values with those obtained by radioimmunoassay are reported. Results on the increases of oestradiol and oestriol in the serum during pregnancy are also reported.     

Prepation of poly(N-isopropylacrylamide)-grafted silica gel and its temperature-dependent interaction with proteins

Poly(N-isopropylacrylamide) oligomer was immobilized onto a silica gel surface. The gel adsorbed a hydrophobic protein γ-globulin (IgG) at 37°C, however, did not adsorb IgG at 24°C. The adsorbed IgG at 37°C was adsorbed by lowering the temperatue, No adsorption of a hydrophilic protein bovin serum albumin (BSA) onto this matrix was observed at 37°C nor 24°C.     

Stereocontrolled synthesis of piperidine-condensed tricyclic carbapenems (5-azatrinems) and their antibacterial activities

Stereocontrolled synthesis of tricyclic carbapenem (5-azatrinem) derivatives 4, in which a piperidine ring is condensed to the carbapenem skeleton, was achieved. The pivotal tricyclic intermediate 2, allyl (8S,9R,10S)-5-(tert-butoxycarbonyl)-10-(R)-1-(tert-butyldimethylsilyl oxy)ethyl]-11-oxo-1,5-diazatricyclo[7.2.0.0(3,8)]undec-2- ene-2-carboxylate, was synthesized starting from an acetoxyazetidinone chiron 6 in a practical manner based on a C-C bond formation reaction between 6 and piperidinone-ester 5, palladium-catalyzed de(allyloxy)carbonylation of 7b and Wittig-type cyclization via an oxalimide 9. Selective deprotection of the N-Boc group of 2 was found to proceed smoothly by treatment with trimethylsilyl trifluoromethanesulfonate and 2,6-lutidine to give the amino compound 3, whose functionalization on the nitrogen atom to derivatives 10 followed by deprotection led to various 5-azatrinem acids 4. These compounds showed potent in vitro activities against gram-positive and gram-negative bacteria.     

Inhibition of mitochondrial respiratory chain by arylthiolated 2,3-ethylenedioxy-1,4-benzoquinones

A series of arylthiolated 2,3-ethylenedioxy-1,4-benzoquinones as a coenzyme Q (CoQ) antagonist was tested for inhibition of succinate oxidase and reduced nicotinamide adenine dinucleotide (NADH) oxidase systems in the mitochondrial respiratory chain. The following characteristics were revealed: (1) 2,3-ethylenedioxy, 5-arylthio and 5,6-diarylthio groups were confirmed to be favorable for inhibition of both systems; (2) these analogs were more effective in the succinate oxidase system than in the NADH oxidase system; (3) 4' substituents on the benzene side ring had little effect on inhibitory activity; (4) the acting sites of these analogs had no strict stereospecificity. The reduced minus oxidized difference spectra revealed that these analogs inhibited the succinate oxidase system at the site between succinate and CoQ, and the NADH oxidase system at the site after cytochrome a + a3, suggesting these analogs might act as antagonists of CoQ in the succinate oxidase system. However, 5-(4'-nitrophenylthio)-2,3-ethylenedioxy-1,4-benzoquinone (If) strongly inhibited only the succinate oxidase system at the site after cytochrome a + a3.