Analogs of pyrimidine mono- and polynucleotides

The corresponding monophosphates, cyclophosphates, and , -diphosphates were obtained by phosphorylation of 1-(1, 4-dihydroxy-2-pentyl) thymine, 1-(1, 3-dihydroxy-2-propyl) uracil, and their derivatives with selective protection of one of the hydroxyl groups. 2-Cyanoethyl phosphate (CEP) in the presence of N, N-dicyclohexylcarbodiimide (DCC), polyphosphoric acid, and pyrophosphoryl chloride were used as phosphorylating agents. The dependence of the yields of the products of phosphorylation of 1-(1, 4-dihydroxy-2-pentyl) thymine with CEP on the ratio of the reacting substances and the reaction time was studied. The monophosphates were cyclized under the influence of DCC. In the case of 1-(1, 3-dihydroxy-2-propyl) uracil 1-phosphate a dimeric phosphate was obtained in addition to a cyclophosphate. The acid hydrolysis of the cyclophosphates was investigated.See [1] for communication V; see [2] for a preliminary communication.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 678–683, May, 1978.     

PHOTOTROPISM–THE NEED FOR A SENSE OF DIRECTION?

Abstract— The ill defined nature of the conceptual framework used to guide research on phototropism is a handicap to progress. It is argued that some of the central concepts, such as the stimulus perception-transduction-response chain, have not given a useful sense of direction. Likewise the arguments as to whether hormones are involved in phototropism have now become a distraction. A constructive phase is now needed, building on an agreed framework. There is an urgent need to identify the universal elements of phototropism and to distinguish those elements from the ones which apply only in specialised cases.     

Polymérisation anionique amorcée par les composés lamellaires du graphite et du lithium

In the present work, we use the binary insertion compound LiC₁₂ to polymerize styrene, methyl methacrylate, butadiene, isoprene, and to copolymerize isoprene and styrene in various hydrocarbon solvents (aromatics and aliphatic) and etheral solvents. We show that the styrene polymerization in aromatic solvents gives better yields than in the etheral solvents, the polymer being atactic. Methyl methacrylate does not polymerize in toluene but does so completely in DME. More generally, the yields of polymerization are better with KC₃₇ than with LiC₁₂ because of the different capacities of the monomer to get into the carbon layers. The polymerization of dienes with LiC₁₂ shows that the microstructures of the polymer obtained in π-or n-donor solvents are similar to the ones obtained by homogenous polymerization with Li cation in such solvents. However, for isoprene in cyclohexane, the results are different. The isoprene styrene copolymers are statistical ones and the mean length of styrene blocks is less than 5. The monomer interaction with the insertion compound and the growing chain geometry between the carbon layers are the facts which control either the stereospecificity of the polymerization or the selectivity of the copolymerization.     

Synthesis of (±)-biotin from a substituted 2,3-dehydrothiophane

(±)-Biotin has been synthesized from a mixture of cis- and allo-trisubstituted dehydrothiophanes by a scheme providing for the easy elimination of the accompanying allo-substituted thiophane in the form of an intermediate and not as the final isomeric allo-biotin. The imidazoline ring of biotin is formed from a dialkoxy-carbonyldiaminothiophane under the conditions of partial hydrolysis of one of the protective groups with the elimination of phosgene from the scheme of synthesis.All-Union Scientific-Research Vitamin Institute, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 220–223, March–April, 1981.     

Origin of the lower critical flocculation temperature in polymer colloids stabilized by polydimethylsiloxane

Summary It has recently been reported (6, 7) that poly(methyl methacrylate) particles that are sterically stabilised by polydimethylsiloxane flocculate on cooling when dispersed in short chain n-alkanes. Since the LCFT was reported to be essentially independent of the nature of the dispersion medium, it was postulated (2) that incipient flocculation of these particles was caused by crystallisation of the polydimethysiloxane chains, which would have allowed the attractive van der Waals forces to become operative. This hypothesis has now been confirmed by low temperature X-ray studies.

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Zusammenfassung Von (6, 7) wurde kürzlich mitgeteilt, daß Poly(methylmethacrylat)-Teilchen, die mit Polydimethylsiloxan sterisch stabilisiert sind, in kurzkettigenn-Alkanen als Dispersionsmittel ausflocken. Da die LCFT im wesentlichen unabhängig von der Natur des Dispersionsmediums ist, wurde von (2) angenommen, daß die beginnende Ausflockung dieser Teilchen auf eine Kristallisation der Polydimethylsiloxan-Ketten zurückzuführen ist, bedingt durch die wirkenden van der Waals-Anziehungskräfte. Diese Hypothese wurde nun durch Röntgenuntersuchungen bei tiefer Temperatur bestätigt.

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