Hisashi Mizutani

Ionic chiral handle-induced asymmetric synthesis in a solid state Norrish type II photoreaction

Abstract Irradiation of crystals of salts formed between 4-(2,4,6-triisopropylbenzoyl)benzoic acid ( 1a ) and various optically active amines is shown to lead to optically active Norrish type II photoproducts in low to moderate enantiomeric excesses, a process in which the ammonium ion has acted as an “ionic chiral handle.” X-ray crystallography reveals that the salts crystallize with two independent, mirror image-related molecules of the benzophenone moiety in the asymmetric unit, and this is suggested to be the source of the low ee s observed.

Two-Molecule Crystals Between Nitroanilines and Nitrophenols

Abstract Slow evaporation of a 1: 1 or 1: 2 molar solution of p-nit roaniline and p-nitrophenol in a mixture of dichloromethane and n-hexane deposited two kinds of single crystals which were mechanically separated: 2: 1 molecular crystal A and 1: 3 molecular crystal B. In a similar manner a 1: 1 or 2: 1 molar solution of m-nitroaniline and m-nitrophenol in a mixture of chloroform and petroleum ether deposited the single crystals of 2 : 1 molecular crystal C. The crystal structures of A, B and C were found to be isomorphic to those of p-nitroaniline, p-nitrophenol (b form) and m-nitroaniline, respectively. The characteristics of the crystal structures of A, B and C are discussed.

Porcine kidney d-amino acid oxidase: the three-dimensional structure and its catalytic mechanism based on the enzyme–substrate complex model

Abstract The three-dimensional structure of porcine kidney d -amino acid oxidase (DAO), an FAD-dependent oxidase, has been solved by X-ray crystallography. The overall structure is a dimer, subunits of which are correlated by a non-crystallographic two-fold axis. Each subunit comprises two domains, ‘αβ domain’ and ‘pseudo-barrel domain’. The coenzyme FAD is in an elongated conformation and is bound at the N -terminal βαβ dinucleotide binding motif. The active site is located in the boundary region between the two domains. The crystal structure of DAO in complex with a substrate analog, o -aminobenzoate, was also solved and is used for modeling the DAO- d -leucine complex, i.e. Michaelis complex, by means of molecular mechanics simulation. The Michaelis-complex model provided structural information leading to two alternative hypothetical mechanisms for the reductive half-reaction of DAO. These two hypotheses characterize themselves by electron transfer from the lone-pair orbital of the substrate amino nitrogen to flavin C(4a) and by proton transfer from the substrate α-position to flavin N(5) which acts as a catalytic base.

Single crystal to single crystal enantioselective [2 + 2] photodimerization of cyclohex-2-enone as an inclusion complex with (?)-1,4-bis[3-(o-chlorophenyl)-3-hydroxy-3-phenylprop-1-ynyl]benzene

Crystals of (?)-1,4-bis[3-(o-chlorophenyl)-3-hydroxy-3-phenylprop-1-ynyl]benzene (4) with two equivalents of cyclohex-2-enone (1), forming inclusion complex 5, have been photoirradiated to give the 1 : 1 complex 6 in a single crystal to single crystal enantioselective [2 + 2] photodimerization reaction in 100% yield without collapse of the crystalline lattice of the inclusion complex. The mechanism has been elucidated by X-ray crystal structure analysis

X-Ray Study of Asymmetric Photoreaction of 2,4,6-Triisopropyl-4′-Carboxybenzophenone

Abstract 2,4,6-Triisopropyl-4′-carboxybenzophenone was converted to the cyclobutenol derivative with the optical yield of e.e.=30% by the irradiation of its salt complex with L-prolinol. This solid state reaction proceeds without the decomposition of the crystal and the structures of the salt crystals before and after irradiation were determined using the X-ray method. In the asymmetric units of both structures, there are two independent molecules, which are related by pseudo glide plane. This pseudo symmetric arrangement of the two molecules is due to the weak chirality of L-prolinol and is responsible for the low optical yield of the reaction.

Inclusion Behavior of Bis (hydroxydiphenylmethyl)cyclohexane as a Potential Host Compound

Abstract The diol host, trans-1,4-bis(hydroxydiphenyl-methyl)cyclohexane has a cyclohexane ring as a rigid framework and a bulky hydroxydiphenyl-methyl group at both ends of the molecule. This host showed a good inclusion ability to form complex crystals with a variety of guest molecules. The complexes with MeOH, acetone, THF, DMF, MeCN and DMSO were obtained as single crystals suitable for X-ray crystallographic study. X-ray structure determination of these crystals clarified that the host:guest complexes show that the guest-dependent polymorphism and crystal structures are classified into five groups. The shape and size of a guest seem to determine the molecular packing in the complex crystal. The guest molecules are included in the columns or cages formed by the hydrophobic groups (benzene and cyclohexane rings) of the hosts, and hydrogen bonded to OH groups of the hosts.

Exceptionally Persistent Nitrogen-Centered Free Radicials. Magnetic Behaviour and X-Ray Crystallo Graphy Structures of N-(Arylthio)-2-Tert-Butyl-4,6-Diarylphenylaminyl and N-(Aryl-Thio)-4-Tert-Butyl-2,6-Diarylphylphenylaminyl Radicals

Abstract The generation, isolation, X-ray crystallographic, structures, and magnetic behavior of N-(arylthio)-2-tert-butyl-4,6-diarylphenylaminyls (2) and N-(arylthio)-4-tert-butyl-2,6-diarylphenylaminyls (3) are described. Radicals 2 and 3 were generated by PbO2 oxidation of N-(arylthio)-2-tert-butyl-4,6-diarylanilines and N-(arylthio)-4-tert-butyl-2,6-diarylanilines, and seven radicals were isolated as the pure radical crystals. The X-ray crystallographic structures of N-[(4-nitro-phenyl)thio]-6-tert-butyl-2,4-diphenylphenylaminyl and N-[(4-nitrophenyl)thio]-4-tert-butyl-2,6-diphcnylphenylaminyl radicals were determined. The magnetic susceptibility measurements for the isolated radicals were carried out in the temperature range 1.8 – 300 K with a SQUID magnetometer. Among the four radicals studied the two were analyzed by an alternating one-dimensional Heisenberg model with J 1/k = -1.8 (α = 0.86) and -18.2 K (α= 0.16), and the other two were analyzed by a one- dimensional regular Heisenberg model with ...