Favorskii-Reaktion von enolisierbaren Cyclobutanonen: Abhängigkeit der Stereoselektivität von der Abgangsgruppe,der Temperatur und dem Lösungsmittel

Dependence of the Stereoselectivity on the Leaving Group, the Temperature and the Solvent in the Favorskii-Reaction of Enolisable Cyclobutanones The base-induced contraction of enolisable 2-halocyclobutanones is often not stereoselectiv. The cis/trans-isomer ratio in the cyclopropanecarboxylic acid 9 derived from 2,4-cis-substituted cyclobutanones 7 depends on the nature of the leaving group. In addition, the choice of the base, the temperature and the solvent can profoundly affect the stereoselectivity of the Favorskii-reaction. The use of the p-bromophenylsulphonyloxy group as leaving group and an inhomogenous reaction medium leads exclusively to cis-carboxylic acid 9 .     

Synthesis und Reaktivität von Dimethylaminoalkylidenaminooxy-arsinen

Synthesis and Reactivity of Dimethylaminoalkylideneaminooxiarsines The reactions of As[N(CH₃)₂]₃ with oximes result in the formation of the oximates [(CH₃)₂N]₂AsONCRR′, (CH₃)₂N As(ONCRR′)₂ and As(ONCRR′)₃. The eleavage of the As-N-bond with alcohols, thiols and diols are described. The reactions of CH₃As[N(CH₃)₂]ONCRR′ with water, amine and alcohols are examined. IR-and ¹H-NMR-spectral data are presented.     

Zur Problematik der Peptidsynthese an Trägern: Beitrag eines neuen Verfahrens mit löslichen Trägern

A new procedure for the synthesis of peptides on a soluble carrier is described. It relies on gel filtration for the removal of low molecular weight reactants from the peptide-polymer complex after each cycle. The advantages of the method are assessed and the insight into the problematics of the carrier synthesis which it provides are discussed. Finally, the use of a monovalent, soluble carrieer molecule of defined chemistry is proposed. Such a carrier should reduce the problems of carrier synthesis to the purely chemical ones commonly associated with peptide synthesis.