No abstract

The reactions of malonaldehyde with guanosine and 2′-deoxyguanosine proceed slowly under acidic conditions to give new pyrimidopurine nucleosides, 3a and 3b, respectively. These compounds emit strong yellow fluorescence and are hydrolyzed by NaOH into malonaldehyde and guanosine from 3a (2′-deoxyguanosine from 3b). From chemical and spectroscopic evidence, these compounds were deduced to be 3-β-d-ribofuranosylpyrimido[1,2-a]purin-10(3H)-one (3a) and 3-(2-deoxy-β-d-erythro-pentofuranosyl)pyrimido[1,2-a]purin-10(3H)-one (3b). No products were detected in the reaction mixture of malonaldehyde with 1-methylguanosine, adenosine, cytidine, uridine, thymidine, 2′-deoxyadenosine, or 2′-deoxycytidine.

Die Reaktion von Malonaldehyd (I) mit Guanosin (IIa) bzw. T‐Desoxyguanosin (IIb) unter sauren Bedingungen führt zur Bildung der stark gelb fluoreszierenden Titel‐Nucleoside (III).

It was found that , -diisopropenyloligopropylene (Mn = 3300-4800) is prepared as the nonvolatile oligomers isolated from the polymer residues resulting from the thermal degradation of isotactic polypropylene at 370 °C. Their structures were determined by and 13C NMR spectroscopies in regard to the reactive end groups. Both the terminal vinylidene double bonds composed of an isopropenyl end group [CH2=C(CH3)-] and the saturated end group [CHaCI^CI^CHCCHa)-] were mainly detected with a molar ratio of about 9:1. The average number of isopropenyl end groups per molecule (ft) is about 1.8, and therefrom it is indicated that about 80 mol % of the oligomer molecules is symmetric a,co-dieneoligomer having two terminal isopropenyl groups. This oligopropylene retains highly the stereoregularity (microtacticity) of the original polymer and has a sharper dispersity of molecular weight (MJMn•. ca. 1.5) than the original polymer, in spite of lower molecular weights and Tm (ca. 150 °C). This compound is useful as a new telechelic oligomer. These oligomers are considered to be formed by the intramolecular hydrogen abstraction (back-biting) of secondary terminal macroradicals followed by ß scission at the end of the main chain (eq 3) and the intermolecular hydrogen abstraction of secondary terminal volatile radicals (eq 4), which are formed by the back-biting and other elementary reactions, followed by ß scission.

No abstract