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Investigations in the Biosynthesis of the Pigments of Life: Calculations on the Formation of Uroporphyrinogen III from Hydroxymethylbilan and Description of a New Mechanism for the D‐Ring Inversion
Author(s) -
Tietze Lutz F.,
Geissler Holger
Publication year - 1993
Publication title -
angewandte chemie international edition in english
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 0570-0833
DOI - 10.1002/anie.199310401
Subject(s) - tetrapyrrole , chemistry , stereochemistry , cationic polymerization , sigmatropic reaction , ring (chemistry) , inversion (geology) , computational chemistry , organic chemistry , biology , enzyme , paleontology , structural basin
The direct formation of a spiro tetrapyrrole intermediate from hydroxymethylbilan ( 1 ) is energetically less favorable than the formation of a cationic σ complex in the first step of the cyclization to form uroporphyrinogen III ( 2 ) [Eq.(a)]. This was shown by calculations on model compounds (A, P = H or Me). The preferred mode of cyclization in the biosynthesis of 2 , which proceeds by inversion of the D ring, can be formulated as an alternative mechanism and has stereoselective H abstraction and [1,5] sigmatropic shifts as key steps. P = (CH 2 ) 2 CO 2 H, A = CH 2 CO 2 H.