Ring contraction of hydroporphinoid to corrinoid complexes.
Crystalline nickel(II) and dicyanocobalt(III) complexes of a racemic 1,2,2,7,7,12,12,17,17,20-decamethyl-20-hydroxy-1,2,3,7,8,12,13,20-octahydro- 17H-porphyrin rearrange to the corresponding complexes of racemic 19-acetyl-1,2,2,7,7,12,12,17,17-nonamethyl-trans-corrin on melting (approximately 290 degrees C and 260 degrees C, respectively). The nickel(II) 19-acetylcorrinate formed in this way is shown to deacetylate to racemic nickel(II) 1,2,2,7,7,12,12,17,17-nonamethyl-trans-corrinate on treatment with 2 M KOH. These reactions are being studied as potentially biomimetic chemical models for the elusive ring contraction step in vitamin B(12) biosynthesis.
Laboratory of Organic Chemistry, Eidgenössische Technische Hochschule Zürich, Universitätstrasse 16, CH-8092 Zürich, Switzerland.
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Rasetti
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Pfaltz
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Kratky
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Eschenmoser