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Lipophilic Functionalized Cobyrinic‐Acid Derivatives. Part 1. Cobester α‐monoacids (α,α,α,β,β,β‐hexamethyl α‐hydrogen Co α, Co β‐dicyanocobyrinates)
Author(s) -
Kräutler Bernhard,
Caderas Christian,
Konrat Robert,
Puchberger Michael,
Kratky Christoph
Publication year - 1995
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19950780306
Subject(s) - chemistry , sulfuric acid , hydrolysis , aqueous solution , crystal structure , hydrogen , stereochemistry , single crystal , solid state , crystallography , organic chemistry
The four α,α,α, β,β,β,‐hexamethyl α‐hydrogen Co α, Co β‐dicyanocobyrinates 2b, d–f , with a free b‐, d‐, e‐ , and f ‐propionic‐acid function, respectively, were prepared by partial hydrolysis of heptamethyl Coα, Coβ ‐dicyanocobyrinate (cobester; 1 ) in aqueous sulfuric acid. The cobester monoacids 2b, d–f were obtained as a ca. 1:1:1:1 mixture which was separated. The monoacids were purified by chromatography and isolated in crystalline form. The position of the free propionic‐acid function was determined by an extensive analysis of 2b, d–f using 2D‐NMR techniques; an analysis of the C,H‐coupling network topology resulted in an alternative assignment strategy for cobyrinic‐acid derivatives, based on pattern recognition. Additional information on the structure of the most polar of the four hexamethyl cobyrinates, of the b ‐isomer 2b , was also obtained in the solid state from a single‐crystal X‐ray analysis. Earlier structural assignments based on 1D‐NMR spectra of the corresponding regioisomeric monoamides 3b, d–f (obtained from crystalline samples of the monoacids 2b, d–f ) were confirmed by the present investigations.