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The ever increasing importance of physical methods in the elucidation of the structure and configuration of carotenoids is reviewed. The use of solvent partition, chromatography, X-ray crystallography, infra-red spectroscopy and optical rotary dispersion are briefly discussed. Special emphasis is given to the application of absorption spectroscopy and to 220 MHz proton magnetic resonance spectroscopy of carotenoids.Mass spectroscopic studies of the characteristic fragmentation of the carotenes, and a possible mechanism for the fragmentation of the polyene chain, are discussed in detail.

Suunrnary.A stereosclectivc synthesis of ( &)-abscisic acid (7) is described in which &cis 3-methylpent-2-en-4-yn-1-01 (2) is used t o introduce the 2-&, 4-tuans geonictry.Abscisic acid, a widely distributed natural plant-growth regulator [l] [a] is the dextrotatory (1's)-enantiomer of the 2-cis,4-trans acid 7 [ 3 ] . Its 2-trans,4-trans isomer is stated to have little or no biological activity, though both geometrical isomers are readily converted into an equilibrium mixture (ca. 1 :1) of the two forms on irradiation [I] [2].The racemate of abscisic acid, and that of its 2-trans,4-trans isomer, were first synthesised by Cornforth et al. [4]. Their starting materials were the 2-cis (8) and 2-trans forms respectively of dehydro-8-ionylidene-acetic acid, which can be separated by fractional crystallisation [5]. Others We now describe an alternative, stereoselective, route to racemic abscisic acid Anionotropic rearrangement of 3-methylpent-1-en-4-yn-3-01, formed by condensation of methyl vinyl ketone with acetylene, forms a mixture of 3-methylpent-2-en-4-yn-1-01s [12]. The predominant cis isomer 2 may be separated by fractional distillation 1131, and provides a convenient starting material for introducing the required configuration.Reaction of the lithium derivative of the cis isomer 2 with the ketone 1 derived from isophorone 1141 gave the expected 2-cis compound 3. This on reduction with sodium bis-(2-metlioxyethoxy-)-aluminium hydride (151 then furnished the 2-cis-, 4-trans-diene-diol 4 which, without purification, was treated with acid to give the dihydroxy-ketone 5 . Allylic oxidation 01 the primary liydroxyl group with manganese dioxide gave the aldehyde 6 which, on further oxidation with silver oxide, yielded (4:)-abscisic acid.With the exception of the intermediate 4, all products were isolated as crystalline solids. Their NMR. sFectra confirmed the given stereochemical course of the reactions. The C(4) and C(5) protons in the conjugated dienes 5, 6 and 7 gave rise to ABquartets, and the coupling constants ( J = 16 Hz) established the trans configuration of the 4,5-double bonds. The deshielding observed with the /I-methyl bands in the aldehyde 6, the acid 7 and its methyl ester was characteristic of 2 4 structures [16].[ll]. Experimental PartReactions were carried out in an inert atmosphere, and solvents mere evaporated under reduced pressure. UV. spectra were run in ethanol, and NMR. spectra at 60 MHz in deuteriochloroform, unless the contrary is indicated. Selected MS. lines only are quoted.2-cis-3-Methyl-5-(4'-ethyletzedioxy-l '-hydroxy-2', 6', 6'-trimethylcyclohex-2'-en-l '-yl) -pent-2-en-4-yn-7-ol (3). Lithium (16.4 g) mas addcd in small portions (of ca. 1 g) to a solution of ferric nitrate (0.5 g) in liquid ammonia (2 1). After the disappearance of the blue colour, indicating the completion of the conversion of lithium into lithamide, cis-3-methylpent-2-en-4-yn-1-01 (2) (99 g ) in ether (100 nil) was added slowly. The ammonia was allowed to evaporate and replaced by ether (1 1). A solution of 4-et...

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3-0-Methyl-4,6-benzal-cc-methyl-~-altropyranosid (IV) wurde von CrO, inPyridin erst in der Hitze angegriffen. Dabei liess sich in ca. 30% Ausbeute ein krist. Dehydrierungsprodukt gewinnen, das als 2-0xo-3-0-methyl-4,6-benzal-~-arabohexopyranosid (VII) identifiziert werden konnte. Ausser der Dehydrierung der sekundaren HO-Gruppe an C-2 was sornit Isornerisierung an C-3 erfolgt. Reduktion dieses Ketons mit NaBH, fuhrte zurn bekannten 3-0-Methyl-4,6-benzal-cr-methyl-nglucopyranosid (VIII) .Institut fiir Organische Chemie der Universitat Base1 Welkstoffe und AntibiotikaSynthese von 2,4-Dimethoxy-6-hydroxy-9,1O-dihydrophenanthren \'on E. Hardegger, N. Rigassi, J . Seres, Ch. Egli, P. Muller und K. 0. Fitzi Herrn Professor Dr. TH. POSTERNAK zum 60. Geburtstag gewidmct (2. I X . 63) 29. Mitteilungl) Aus Orchideenknollen, die mit dem Kranklieitserreger Khizoctonia re$ens BERN. infiziert waren, wurden bisher u. a. zwei Verbindungen C,,H,,O,, das Orchinol und dasLoroglossol isoliert 2). Orchinol, ein induzierter Abwehrstoff aus erkrankten Knollen von Orchis mititaris, wurde als 2,4-Dirnethoxy-7-hydroxy-9,10-dihydrophenanthren (I) erkannt 7,). Dem biologisch inaktiven Loroglossol scheint, auch biogenetisch begrundet , ), die Konstitution des 2,4-Dirnethoxy-5-hvdroxy-9,lO-dihydrophenanthrens (11) zuzukommen.Fur Versuche zur Ermittlung der Strukturspezifitat der antibiotischen Wirksarnkeit erschien die Herstellung des zu Orchinol (I) und Loroglossol (11) isorneren 2,4-Dimethoxy-6-hydroxy-9,lO-dihydrophenanthrens (XIX) wunschenswert , welches sich von I und I1 lediglich durch eine andere Stellung der phenolischen Hydroxylgruppe unterscheidet.Die hiezu notwendigen Versuche folgten einerseits der von WALKER4) beschriebenen eleganten Synthese analoger Verbindungen und gleichzeitig den in dieser Arbeit