Utificial enzyme models with porphyrin, stemids and calixarenes as buildq units. wherein h v ~ kinds of novel enzym models of stemid+doporphynn and &ne-metaU&yrin have been gynfhesized and employed as c y t o c h P450 modeling. 'Ihese &&tic systems exhibited tugh catalytic selectivity and efiiciency in oxidation of olefins (styrene, cyclohsrene) and h y -(iS0pmpy-e) 88 well as phenol ( P -b n e . d i -01). 'Ihe e x d e n t catalytic p m p q stems mainly fmm hydmphobic dect and multiple I.ecognition sites that lead to cooperative catalysis.
Keywolds
Enzyme model, stemid, cdixmne, metaUoptnphyrin, bicrmetallopoIphyrin.
Enzyme catalyzed reactions often p d with exceptionally high selectivity and high efficiency under mild conditions. ' However, disadvantages of using enzyme catalysts am their high cost, their instability to high temperatwe ( > w ) C ) , and the difficulty of recovery."2'lhus, the study of artificial enzyrnes has been becoming one of the most challenging and attractive subjects in modem bimrganic chemistry.
The recent achievement indicates that many enzyme models offer hi& selectivity, high efficiency and facility for recovering.
Metalloporphyrin plays an important role in biological systems, such as redox reaction, electron transfer, oxygen transport, and charge separation etc . Metalloporphyrin also s e ~~e s
as a new type of catalyst, showing high catalytic activity in many reactions such as oxidation, reduction and polymerization.
We have been interested in the synthesis of novel types of modified-porphyrins as artificial enzymes.
Among the five mpi~ments for the design of a good enyme model, the hydrophobic binlmg sites or matrix providing for substrate am particularly important .4 Steroids have hydrophobic planar fiamewodc and calivarenes may pmvide hydrophobic cavities of various sizes. Furthermore, both of them are readily modified and can be connected with multiple catalytic centers. 'lherefore it can be expected that steroidor caliuarene-modified metaUoporphynns should have much better catalytic p q r t i e s .
Our biomimetic studies involve the design and synthesis of enzyme-models and examination of their catalytic pmpexties . Several aspects of such effom am pmnted bridy as follows.