((Push-Pullr Acetylenes as Reagents for Peptide Synthesis Summary A series of 'push-pull' acetylenes 1 is easily available from the corresponding 'push-pull' olefins by a simple bromination-dehydrobromination sequence. The versatility of the acetylenes with regard to peptide synthesis is discussed.

(7.11.77) Synthesis of benzofulvenes and dibenzofulvenes via 1-chloroalkyl-acetates Summary 1,2-Benzofulvene (6a) and 1,2,3,4-dibenzofulvene (7a) as well as the corresponding 6-methyl-and 6-phenyl-derivatives are prepared by reaction of sodium indenide and sodium fluorenide with l-chloroalkyl acetates (3), followed by elimination with KOC (CH,),. The over-all yields are comparable with the results of the fulvene series and are in most cases considerably higher than the yields of the Thiele-method. Im Rahmen von Versuchen zur Herstellung von Nonafulven [I21 stellte sich die Frage, ob sich die von uns entwickelte Synthese von Fulvenen iiber l-Chlor-

Push-pull'-acetylenes 1 are excellent reagents for peptide synthesis: Addition of 'push-pull'-acetylenes to solutions of N-protected amino acids (or vice versa) gives enol esters 5, which react selectively with the amino function of a second amino acid. In this way serine, tyrosine, 4-hydroxyproline, cysteine as well as histidine are linked to form dipeptide esters without protection of the second functional group (OH, SH or NH). The amount of racemization is very low. Similarly tri-as well as tetrapeptides are available. The versatility of the reaction is discussed. Einleitung. -ccPush-Pull))-Acetylene 1 [5][6] setzen sich mit Carbonsauren unter schonenden Bedingungen annahernd quantitativ zu 3-Acyloxy-acrylamiden (2) urn [ 11 [5] [7] (Schema 1). Da die Addition der Carboxylgruppe sehr selektiv verlauft [ 11, sind auch Carbonsauren, die weitere funktionelle Gruppen tragen [2] [8], zur Re-

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Amide Synthesis by Means of 'Push-Pull'-AcetylenesSummary 'Push-pull'-acetylenes react easily with carbon acids. Addition of amines to the crude reaction mixture gives amides in an excellent yield by a simple one-pot procedure. Because of the high selectivity of the acetylenes 1 towards carboxylic functions and of the high selectivity of the enol esters 4 towards amine functions, 'pushpull'-acetylenes could be excellent reagents for peptide synthesis.