Chemie der α‐Aminonitrile 1. Mitteilung Einleitung und Wege zu Uroporphyrinogen‐octanitrilen

Abstract

Chemistry of α‐Aminonitriles I: Introduction and Pathways to Uroporphyrinogen‐octanitriles. An introduction to experimental studies on the chemistry of α‐aminonitriles potentially relevant to the problems of prebiotic chemistry is presented. The framework of conditions wherein the investigation is chosen to be carried out implies both molecular oxygen and ‐ whenever feasible ‐ water to be excluded from reaction conditions. This study focusses on 2‐amino‐2‐propenenitrile ( 3 ) ( Scheme 6 ) as central starting material of reaction sequences which aim at the nitrile forms of proteinogenic amino acids as well as at the aza forms of building blocks of biological cofactor molecules as their targets ( Scheme 5 ). Schemes 13,16,23 as well as 25 and 26 summarize reaction sequences by which 3 is transformed within the defined framework of conditions into the thermodynamic (statistically controlled) mixture of the four isomeric uroperphyrinogen‐octanitriles 57–60 . HPLC's of such mixtures document the dominance of the least symmetrical isomer whose constitutional pattern of peripheral substituents happens to be the one percent in all biological porphinoids. Preparative procedures for the synthesis of 3 (Scheme 9), the β,β‐disubstituted pyrrol‐nitriles 30,53 and 54 ( Scheme 19 ) as well as the porphyrinogenoctakis(propionitrile) and‐octakis(acetonitrile) 65 and 66 , respectively ( Scheme 24 ) are given.