Seiji Sawada

The chemistry of zerumbone. Part 5: Structural transformation of the dimethylamine derivatives

Abstract Zerumbone ( 1 ) and its 6,7-epoxide ( 2 ) react with ammonia and dimethylamine regio- and stereospecifically, affording monoamines 3 , 4 , 7 and 8 . All adducts have the same relative configuration at C2 and C3. The conjugate amination is thermodynamically controlled to arrive at a single diastereomer. At 15°C 7 reacts with cyanide to give aminonitrile 10 as the single product, while at 30°C, acyclic aminonitrile 11 is also formed. The reaction with 8 affords at 0°C bicyclic aminonitrile 12 of the asteriscane skeleton, while at 30°C or higher temperature, mixtures of 12 and tricyclic nitriles 13 and 13′ are obtained. Refluxing of 7 , 8 and 10 in aqueous acetonitrile promotes scission of the zerumbone ring by retro-Mannich reaction to provide acyclic aldehydes 16–18 , respectively. The dimethylamino group of 7 , 8 and 10 is eliminated stereospecifically by Cope- and base-catalyzed eliminations to regenerate the zerumbone skeleton in the products 1 , 2 and 21 . Cope elimination of 12 results in a mixture of 13 and 13′ by deaminative transannular etherification.

Fluorescent rotors and their applications to the study of G-F transformation of actin

New fluorescent rotor molecules having hydrophilic functional groups, which are derivatives of p-(N,N-dialkylamino)benzylidenemalononitrile, were synthesized. Their properties as fluorescent rotors were confirmed by an observation of solvent viscosity-dependent fluorescence. Incorporation of hydrophilic groups into the molecules increased the solubility of fluorescent rotors in aqueous media; the application of the compounds to biochemical systems became feasible as a consequence. To demonstrate this applicability, we attempted to monitor the G-F transformation of rabbit skeletal muscle actin with these newly synthesized compounds. All the compounds carrying a malononitrile moiety showed greater fluorescence in F-actin. Among them, 1-(2-hydroxyethyl)-6-[(2,2-dicyano)vinyl]-2,3,4-trihydroquinoli ne gave the best result by the criteria of the difference in fluorescence quantum yield for G- and F-actin, solubility, and stability of the compound. The method has the major advantage of not requiring covalent modification of actin.

Stereochemistry of ammonia elimination from l-tyrosine with lphenylalanine ammonia-lyase

Abstract The trans stereochemistry was established for the enzymatic deamination by l -phenylalanine ammonia-lyase from Rhodotorula texensis, based on the spectroscopic analysis of the deamination products from stereospecifically labeled l -(3R)-[3- 2 H 1 ] - and l -(3S)-[2,3- 2 H 1 ]tyrosine used as substrate. The exchange of hydrogen on C-2 was not observed during the ammonia-elimination process.

The chemistry of zerumbone. Part 3: Stereospecific creation of five stereogenic centers by double Sharpless oxidation

Abstract The Sharpless asymmetric epoxidation was applied to zerumbol 2 in order to introduce chirality into the readily available achiral sesquiterpene zerumbone 1. Single bisepoxides (+)-3 and (−)-3 were obtained in nearly 100% enantiomeric purity, characterized as the unexpected all erythro configuration by X-ray analysis.

Enzymatic preparation of α- and β-deuterated or tritiated amino acids with l-methionine γ-lyase

Abstract l -Methionine γ-lyase catalyzes the exchange of α- and β-hydrogens of l -methionine and S -methyl- l -cysteine with deuterium or tritium of solvents. The rate of α-hydrogen exchange with deuterium was about 40 times faster than that of the elimination reactions. The deuterium and tritium were exchanged also with the α- and β-hydrogens of the straight-chain amino acids which do not undergo the elimination: l -alanine, l -α-aminobutyrate, l -norvaline, and l -norleucine. No exchange occurs for the d -isomers, acidic l -amino acids, basic l -amino acids, and branched-chain l -amino acids, although α-hydrogen of glycine, l -tryptophan, and l -phenylalanine is exchanged slowly. These enzymatic hydrogen-exchange reactions facilitate specific labeling of the l -amino acids with deuterium and tritium.

Biostereochemistry of histidine metabolism: II. The steric course of ammonia elimination from l-histidine☆

Abstract [2-2H]Urocanic acid was obtained from the enzymatic reaction of racemic and stereoselectively labelled, dl -(±)-(3S): (3R)-[2,3- 2 H 2 histidine with histidase prepared from Pseudomonas striata. The stereochemistry of deamination was assigned to be a stereospecific trans-elimination including pro-R proton liberation from the C-3 position of l -histidine.

Biotransformation of zerumbone by Caragana chamlagu

Suspension cultured cells of Caragana chamlagu (Leguminosae) converted zerumbone (1) into zerumbone epoxide (2) as the intermediate, (2R,3R,7R)-2,3-epoxy-9-humulen-8-one (3) and (2R,3S,7R)-2,3-epoxy-9-humulen-8-one (4) as new sesquiterpenes in 11%, 36% and 21% yields, respectively.

Proliferative and metastatic activities of mouse tumor cells exposed to a strong static magnetic field

Abstract Mouse EL-4 T-lymphoma cells and B16 melanoma cells were incubated in a static magnetic field at 6.34 tesla (T) in NMR sample tubes for various time intervals at 37°C. After being exposed to the magnetic field, the tumor cells were tested for proliferative and metastatic activities. The exposed EL-4 cells and B16 cells proliferated more rapidly than the sham-exposed corresponding control tumor cells. Intravenous injection of the exposed B16 cells into C57BL/6- beige / beige mice, produced a significantly larger number of pulmonary metastatic nodules than injection of the sham-exposed B16 cells. These findings suggest that strong static magnetic fields augment the cell proliferative activity and may promote the metastasis of tumor cells under certain conditions.

Stereochemistry of an α,β-elimination reaction by D-glucosaminate dehydratase

The proton NMR analysis of D‐glucosaminate dehydratase reaction in D2O revealed the incorporation of a deuterium atom at C‐3 carbon of the product, 2‐keto‐3‐deoxy‐D‐gluconate. Based on the chemical shift of C‐3 proton of the product and the coupling constant characteristic for the C‐3 and C‐4 axial‐axial coupling in the 2C5 pyranose conformation, the deuterium is in the pro‐S position. Thus, the dehydration of D‐glucosaminate by the enzyme proceeds in a retention mode at C‐3 carbon. Kinetic parameters show that the rate‐determining step is the abstraction of α‐proton from the substrate.

Stereochemistry of the conversion of serine and tyrosine into pyruvate by tyrosine phenol-lyase

(2S,3R)- and (2S,3S)-[3-3H]serine in D2O and (2S,3R)-[3-2H]tyrosine in HTO were incubated with tyrosine phenol-lyase to give pyruvate which was trapped as lactate; chirality analysis of the methyl group in the products showed that the replacement of the β-substituent in these amino acids by hydrogen had occurred stereospecifically with retention of configuration.