Nikolaus Risch

Photobilin e. Photooxidation von bacteriochlorophyll-e-derivaten

Abstract The blue photooxidation products from metall-free derivatives of bacteriochlorophyll e can be purified without decomposition by reversed phase chromatography. They are identified spectroscopically and chemically as open-chain tetrapyrroles and are named photobilins e.

Chlorophyll B. Totalzuordnung des 13C-NMR-spektrums

Abstract The assignment of all resonances in the 13 C NMR spectrum of chlorophyll b has become possible by using incremental data and special NMR techniques.

Synthesis of carbon-carbon linked porphyrinoligomers by utilization of Heck-type coupling of natural tetrapyrroles

Abstract The Heck type cross-coupling reaction of zinc(II)-monobromodeuteroporphyrin-dimethylester and di- or trivinylbenzene provided Cue5f8C-linked di- and trimeric porphyrins in high yields. The reaction was carried out with palladium(II)-acetate in DMF under phase-transfer conditions.

Application of iminium salts in the synthesis of fused pyridines. Introduction of substituents using ternary iminium perchlorates

Abstract Ternary iminium perchlorates are used as synthetic equivalents for aliphatic and aromatic aldehydes in a complex one pot reaction, providing an easy access to terpyridines with peripheral substituents. According to the proposed reaction mechanism this is the first example of an aminoalkylation of a ketone using this type of iminium salts. Surprisingly, the reaction produces “S-shaped” and “U-shaped” isomers. The distribution of isomeric products seems to be strongly influenced by electronic and/or steric properties of the substituent in the native iminium compound.

Triple (Grob) fragmentation. Retro-mannich reactions of 1-aza-adamantane derivatives

Abstract The first triple (Grob) fragmentation is described. The process (mechanism) involves retro-Mannich reactions. Easily accessible 1-aza-adamantane derivatives 1 are converted to substituted 5-chloro-resorcinols 5 .

Partialsynthese eines stereochemisch einheitlichen bacteriochlorophylls D

The main problem in the synthesis of a stereochemically pure bacteriochlorophyll d is the separation of two “epimeric” key intermediates. This can be achieved by chromatography on a silica gel column coated with the optically active electron acceptor compound (+)-TAPA (7). The purity of the epimers thus obtained is proven by 1H-n.m.r.-spectra.