New Model Porphyrin Complexes Having Asymmetric Functions

1992 Fiscal Year Final Research Report Summary

• Project/Area Number: 02650633
• Research Category: Grant-in-Aid for General Scientific Research (C)
• Allocation Type: Single-year Grants
• Research Field: Synthetic chemistry
• Research Institution: Kogakuin University
• Principal Investigator: OHKATSU Yasukazu Kogakuin Univ.,Engineering, Professor., 工学部, 教授 (20011009)
• Project Period (FY): 1990 – 1992
• Keywords: Cytochrome P-450 / Etioporphyrin / Metaloporphyrin complex / Asymmetric epoxidation / Peptide chains

Research Abstract

Heme proteins have conformations, which hemes are present in asymmetric space which proteins provide, are catalyze many biological reactions. Cytochrome p-450 is one of heme proteins. Recently many models of this enzyme have been proposed, but none of them contain segments similar to protains. In this study, new asymmetric porphyrin complexes having such segments are synthesized and applied to asymmetric epoxidations of styrene as is performed by Cytochrome P-450. Based on the results, furthermore, the function of proteins in home proteins is also discussed.
The complex having, for example, four long peptide chains(PCs) was synthesized by nitrating zinc etioporphyrin with a zinc(II) nitrate hexahydrate-acetic anhydride system, and eliminating zinc with perchloric acid, followed by the introduction of iron in place. Then nitrogroups of the complex were reduced to amino groups by means of NaBH in the presence of Pd/C catalyst, and finally the resulting amino complex was allowed to react w ith gamma-BLG-NCA to from the intended model complex.
In model reactions, the complex having three PCs of, for example, gamma-BLG catalyzed, model reactions effectively, but the e.e. of styrene oxide obtained was rather low (for example, e.e. 11.2% at yield of 60.3%). However the model of four PCs increased the e.e.considerably without any remarkable decrease in chemical yields (for example e.e.53.8% at yield of 52.6%). The length of peptide chain also affected asymmetric induction dramatically ; the e.e. increased from 16.9% to 53.8% with similar chemical yields when numbers of gamma-BLG in the peptide chain increased from 2.0 to 4.4. These facts suggest that asymmetric induction in not performed by simple steric controls, but by the conformation change of peptide chains when the substrate of styrene is intaken, resulting in the formation of conformation more preferable for asymmetric epoxidation. The model complexes proposed by this research can be said to resemble cytochrome P-450 in many aspects.