Butenandt

The first, and to this writing still only case of a ketone a-cleavage-recombi-nation sequence in the steroid field was reported by Butenandt, who found that 17-ketones epimerize at C-13. Ultraviolet irradiation of either stereoisomer produces an equilibrium mixture in which the thermodynamically more favored 13a-compound cf. (15)] with cw-fusion of rings C and D predominates at room temperature. As ultraviolet absorption energies and intensities of the two isomeric ketones are practically identical, the equilibrium composition depends largely on the rate of the competing recombination process from (14). For further examples of the photoisomerization at C-13 of 17-ketosteroids, see ref. 8, 12, 15 and 43. 

Example Mali do (15, R=Pr-n) was used by Butenandt in his original synthesis of bombykol Cp iSf ) (16). Wittig disconnection of the tvans double bond requires cie allylic ylid (17), It is easier to use acetylenic ylid (18) and half aldehyde (19) in this step because el availability,... 

Many different functions of pheromones have been found since Butenandt. Aggregation pheromones attract both sexes to a special location, while sex pheromones are offered by one sex only to attract or arouse the other one. Trail pheromones used by ants mark food trails and alarm pheromones change the state of alertness of conspecifics. These are only some of the functions pheromones can have, and similar different functions can be found in allelochemicals as well. 

Butenandt, A., Wolff, A. Ber. Deut. Chem. Ges. 72, 1121 (1939) sowie nachfol-gende Veroffentlichungen dieses Arbeitskreises. 

H. Knozinger, Department Chemie-Physikalische Chemie, Universitat Miinchen, Butenandt Strasse, 5-13, Haus E, D-81377 Miinchen, Germany (1)... 

Department Chemie-Physikalische Chemie, Universitdt Miinchen, Butenandt Strasse,... 

Ludwig-Maximilians-Universitat Munchen Department Chemie Butenandt Str. 5-13 (Haus D)... 

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