acid (m.p. 176-178') has been prepared by the WITTIG reaction of (deh~~dro-~-ionylidene-ethyl)-triphenylphosphonium bromide and 12-butyl P-formylcrotonnte. Reduction of this acid with lithium-aluminium hydride gave a mixture of all-trms-and 13-cis-vitamin A,, which could be separated by chromatography. The same mixture has been obtained from vitamin A acid according to the first vitamin , U. Schwieter, L. Chopard-dit-Jean, R . Ruegg, M. Kofler und 0. Isler (12. I. G2) 4. Mitteilung') Die drei vorangehenden Mitteilungenl) hatten die Synthese von 6 Reihen isomerer Vitamin-A,-Verbindungen zum Inhalt. In dieser Arbeit werden die physikalischen Eigenschaften dieser Vitamin-A,-Verbindungen beschrieben und mit denj enigen der entsprechenden Vitamin-A-Verbindungen verglichen. .l,-Kcihe A-Reihc I< = CH,OIf, CHO, COOH, COOCH,Untersucht wurden ausser den in den Formeln dargestellten ungehinderten alltrans-Verbindungen 3 weitere ungehinderte Isomere (9-cis, 13-cis, 9,lS-di-cis) sowie 2 Isomere mit sterischer Hinderung (11-cis, 11,13-di-cis).
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