NMR spectra (in [D],DMF) of natural D and synthetic 4 were essentially identical, particularly in the region representing olefinic protons (6 = 5.6-6.8). This, in turn, proves that the the component D is pure all-trans-fecapentaene-14 (4).We have also established that the CI mass spectra of the natural and the synthetic compounds are identical. These spectra, however, show very little fragmentation, and thus are not sufficiently informative.These investigations enable us for the first time to assign the complete structural formulas to two naturally occurring fecapentaenes. The geometry of the CC double bonds may play a role in the degree of mutagenicity exhibited by both types of fecapentaene~.''.~~ Interestingly, the two identified components, all-trans-fecapentaene-12 (3)[91 and alltrans-fecapentaene-I4 (4)['] belong to the most potent mutagens so far known. Their occurrence in human feces and their accessibility by chemical synthesis raise hopes that they might serve to answer the question whether the fecapentanes are carcinogens.

sugars as building blocks for replicating systems, these results direct thinking once again toward ribose itself, and chemical work seeking an improved abiotic synthesis of ribose would be most desirable.(16) Note Added in Proof: In the synthesis of these oligomers, coupling yields were ca. 90% for glycerothymine and >99% for natural nucleosides. The product oligonucleotides were purified by reversed phase HPLC (Nucleosil C-4 column, gradient from 15% to 30% acetonitrile in 0.1 M triethylammonium acetate) prior to the removal of the 5'-trityl groups and detritylated (80% acetic acid). Samples of the oligonucleotides containing the flexible base were digested with spleen phosphodiesterase, snake venom phosphodiesterase, and bacterial alkaline phosphatase. HPLC of the digests showed the expected nucleosides in their expected ratios.

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Verbindungen vom Typ RLi mit RPhCC, PhCH2, Ph, CH2CHCH2, Alkyl, Me3SiCH2, PhCH2OCH2 usw. lassen sich wie unten skizziert auf einem Umweg leicht bei tiefen Temperaturen erzeugen. Bei einer Eintopf‐Variante werden die Telluride direkt aus Alkylhalogeniden und Tellurolaten RTeLi gewonnen. Das Verfahren empfiehlt sich besonders, wenn der konventionelle Lithium‐Halogen‐Austausch nicht möglich ist.