Synthesis of 1,1,3,3,5,5-Hexamethyl-7,7-diorganocyclotetrasiloxanes and Its Copolymers

This paper reports a method for the synthesis of 1,1,3,3,5,5-hexamethyl-7,7-diorganocyclotetrasiloxanes by the interaction of 1,5-disodiumoxyhexamethylsiloxane with dichlorodiorganosilanes such as methyl-, methylvinyl-, methylphenyl-, diphenyl- and diethyl dichlorosilanes. Depending on the reaction conditions, the preparative yield of the target cyclotetrasiloxanes is 55–75%. Along with mixed cyclotetrasiloxanes, the proposed method leads to the formation of polymers with regular alternation of diorganosylil and dimethylsylil units. For example, in the case of dichlorodiethylsilane, 70% content of linear poly(diethyl)dimethylsiloxanes with regular alternation of units can be achieved in the reaction product. Using 7,7-diethyl-1,1,3,3,5,5-hexamethylcyclotetrasiloxane as an example, the prospects of the mixed cycle in copolymer preparation in comparison with the copolymerization of octamethyl- and octaethylcyclotetrasiloxanes are shown.

Genetic loci determining potato starch yield and granule morphology revealed by genome-wide association study (GWAS)

Background It is well-documented that (bio)chemical reaction capacity of raw potato starch depends on crystallinity, morphology and other chemical and physical properties of starch granules, and these properties are closely related to gene functions. Preparative yield, amylose/amylopectin content, and phosphorylation of potato tuber starch are starch-related traits studied at the genetic level. In this paper, we perform a genome-wide association study using a 22K SNP potato array to identify for the first time genomic regions associated with starch granule morphology and to increase number of known genome loci associated with potato starch yield. Methods A set of 90 potato (Solanum tuberosum L.) varieties from the ICG “GenAgro” collection (Novosibirsk, Russia) was harvested, 90 samples of raw tuber starch were obtained, and DNA samples were isolated from the skin of the tubers. Morphology of potato tuber starch granules was evaluated by optical microscopy and subsequent computer image analysis. A set of 15,214 scorable SNPs was used for the genome-wide analysis. In total, 53 SNPs were found to be significantly associated with potato starch morphology traits (aspect ratio, roundness, circularity, and the first bicomponent) and starch yield-related traits. Results A total of 53 novel SNPs was identified on potato chromosomes 1, 2, 4, 5, 6, 7, 9, 11 and 12; these SNPs are associated with tuber starch preparative yield and granule morphology. Eight SNPs are situated close to each other on the chromosome 1 and 19 SNPs—on the chromosome 2, forming two DNA regions—potential QTLs, regulating aspect ratio and roundness of the starch granules. Thirty-seven of 53 SNPs are located in protein-coding regions. There are indications that granule shape may depend on starch phosphorylation processes. The GWD gene, which is known to regulate starch phosphorylation—dephosphorylation, participates in the regulation of a number of morphological traits, rather than one specific trait. Some significant SNPs are associated with membrane and plastid proteins, as well as DNA transcription and binding regulators. Other SNPs are related to low-molecular-weight metabolite synthesis, and may be associated with flavonoid biosynthesis and circadian rhythm-related metabolic processes. The preparative yield of tuber starch is a polygenic trait that is associated with a number of SNPs from various regions and chromosomes in the potato genome.

On the hydrolysis of diethyl 2-(perfluorophenyl)malonate

Diethyl 2-(perfluorophenyl)malonate was synthesized in 47% isolated yield by the reaction of sodium diethyl malonate and hexafluorobenzene. The resulting compound was considered as a starting material for synthesizing 2-(perfluorophenyl)malonic acid by hydrolysis. It was found that the desired 2-(perfluorophenyl)malonic acid could not be obtained from this ester by hydrolysis, neither under basic nor under acidic conditions. Nevertheless, hydrolysis of the ester with a mixture of HBr and AcOH gave 2-(perfluorophenyl)acetic acid in a good preparative yield of 63%. A significant advantage of this new approach to 2-(perfluorophenyl)acetic acid is that handling toxic substances such as cyanides and perfluorinated benzyl halides is avoided.

Synthesis of luminescent polyconjugated compounds with phenyloxadiazole fragments

Synthesis of new asymmetric poly-π-conjugated 1-substituted derivaties of 5,5-dioxodibenzothiophene containing 1,2,3-oxadiazole fragment in the main chain of conjugation and cyclic fragments as the central chromophore are synthesized. The preparative yield of the target compounds was achieved using phosphorus (V) oxychloride as a cyclizing agent. The compounds obtained have high melting points and are blue phosphorescent luminophores.

Porcine Liver Esterase-Catalyzed Hydrolysis of Methyl Tri-O-acetyl-β-D-arabinopyranoside, Methyl Tri-O-acetyl-β-D-ribopyranoside and Methyl Tri-O-acetyl-β-D-ribofuranoside

Methyl 2,3,4-tri-O-acetyl-β-D-arabinopyranoside (1), methyl 2,3,4-tri-O-acetyl-β-D-ribopyranoside (2), and methyl 2,3,5-tri-O-acetyl-β-D-ribofuranoside (3) were deacetylated in porcine liver esterase-catalyzed reactions. Triacetate 1 gave methyl 3,4-di-O-acetyl-β-D-arabinopyranoside in 70% preparative yield while the regioselectivities found for the substrates 2 and 3 were substantially lower. Both the Michaelis constant and maximum rate were calculated for deacetylation of 1, 2, and 3. The results were interpreted using an active site model for the esterase proposed by Jones.

Aluminium chloride induced isomerisation of 1,1,2-trichlorotrifluoroethane and 1,2-difluorotetrachloroethane

Under comparable conditions, the isomerisation of 1,1,2-trichlorotrifluoroethane (I) to 1,1,1-trichlorotrifluoroethane (II) is more difficult than the isomerisation of 1,2-difluorotetrachloroethane (III) to 1,1-difluorotetrachloroethane (IV). Advantageously, III was isomerised to IV in the presence of I or II. The degree of isomerisation of the starting compounds I and III was 95-99%, the preparative yield of IV being 65-74%. The C-F bond energies in I-IVwere derived from correlation diagram and the physico-chemical aspects of the isomerisation are discussed.