Richard Kuhn in kollegialer Verbundenheif gewidmetAus dem Substanzgemisch, das bei der Bestrahlung von Ergosterin mit UV-Licht entsteht, konnte erstmats 1932 ein vollkommen gereinigtes D-Vitamin gewonnen werden. Es erhielt den Namen Vitamin Dz. Vier Jahre spater gelang die lsolierung des naturlichen D-Vitamins (Vitamin D3) aus Fischleberolen. Beide Verbindungen unterscheiden sich chemisch nur durch eine Doppelbindung und eine Methylgruppe i n der Seitenkette. Die D-Vitamine und mit ihnen verwandte Verbindungen geben thermische, photochemische und chemische lsomerisierungsreaktionen, die hier beschrieben werden. SchlieOlich wird zusammenfassend uber die kurzlich gelungene Totalsynthese des Vitamins D3 berichtet. Einleitung

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NC0)4 + 2 (R3Si)zNNa + 2 NaOCN + RASiNCNSiR3 J,l/x [--OSi(OSiR,) (NCNSiR,)-], Die Darstellung eines Tricyanatosilylamins gelang nur iiber : (R3Si)zNNa-(R;Si)zNSiC13 -(R,Si)*NSi(NCO)s (Kp = 81 "C/lTorr).Kohlenmonoxyd wird unter Disiloxan-Abspaltung in Natriumcyanid umgewandelt : CO + NaN(SiR3)z + (CN)-Na+ + O(SiR&.

The radicals of the T2-protein are equal in concentration and spectral frequency to those of other sulfur-free proteins (e. g . gelatin). D-2-Deoxyribose gives a radical yield of G = 4. The radicals produced in the nucleosides do not show a spectrum typical of ~-2-deoxyribose, but spectra which are similar to those of the free bases. Whilst the radical yield of irradiated nucleotides corresponds to that from nucleic acids (G = 2-15), the radical yield in the case of irradiated nucleosides is less (G = 0.4-1.0) and still smaller in the case of the pure nucleic-acid bases (G = 0.1 to 1.0). The radical yield increases particularly strongly on pasing from thymine via thymidine to thymidine-5-monophosphate. Directly after irradiation, the spectrum of the phosphate, like that of thymine, has a large number of lines, but on keeping changes into a quartet, which appears very like that of stored nucleic acid. The radical concentrations in the bases, nucleosides, and nucleotides show a similar dependence on the radiation dose as those in the nucleic acid and all the other substances investigated. It is probable that the primary radiation damage occurs at the thymine unit of the nucleic acid. [Physikalisches Colloquium, Heidelberg (Germany) Birch reduction of 3,4-di-p-anisylhexane-3,4-diol gives a bisenol-ether which is converted into ( I ) by mild treatment with acid. The reaction of ( I ) with alcoholic sulfuric acid aKords a mixture from which a racemate of molecular formula ClsH2202, m.p. 70-71 OC, and with ultraviolet maxima at A = 303 mp. E = 19000, and 1, -224 mp, E = 14300, can be isolated in 30 "/, yield. This compound was shown to have the spiro-ketone structure (2).[ The ratio of acetylenic to olefinic protons was 1:3 and corresponds to the formula of 1 -hexene-3,5-diyne ( I ) . The N M R spectrum excludes all other possible constitutions.The third c 6 acetylene (0.1 %) was separated on polypropylene glycol as stationary phase. Structures (2u) and (2b) were possible according to infrared and mass spectra. Compound (2u) was synthetized from 1,4-pentadiyne-3-01, and (2b) from 1,5-hexadiyne-3-01 (3). The results obtained indicated that truns-3-hexene-l,5-diyne (26) is present in electric-arc acetylene. CHz=CH-CZC--CECH