Hiroshi Kakisawa

Absolute configurations of marine diterpenes possessing a xenicane skeleton. An application of an advanced Mosher's method

By means of Moshers method using 1H NMR spectroscopy at 500 MHz the absolute configurations of marine diterpenes, 7 and 8, have been elucidated.

Elucidation of the absolute configurations of amino acids and amines by the modified mosher's method

Abstract Application of the modified Moshers method to the N -MTPA derivatives of several amino acid esters and acyclic amines indicates that this method may be generally used to determine the absolute configurations of the α-carbons of amino compounds of less than 0.1 mg amount.

Absolute configurations of cytotoxic marine cembranolides; Consideration of mosher's method

Abstract Stereochemistry of the cembranolides 1 and 5 , isolated from the soft coral Sinularia mayi , has been elucidated by means of 2D NMR spectroscopy and X-ray crystallography. The absolute configuration of denticulatolide 6 has been determined by X-ray analysis, and the validity of Moshers method is discussed as to the MTPA esters 3 , 4 , 7 , and 8 .

An allelopathic fatty acid from the brown alga Cladosiphon okamuranus

Abstract An allelopathic substance was isolated from the methanol extract of the brown alga, Cladosiphon okamuranus . Extraction and purification of the active substance was monitored by bioassays against the conchospores of Porphyra yezoensis and Heterosigma akashiwo . The compound was identified as 6 Z ,9 Z ,12 Z ,15 Z -octadecatetraenoic acid and its activity was then tested against 36 species of microalgae. Many of eukaryotes tested were affected at 5 ppm, but prokaryotes were unaffected at 25 ppm. The tetraunsaturated fatty acid exterminated toxic red tide planktons such as Chattonella antiqua at 1 ppm concentration.

Cyanoviridin RR, a toxin from the cyanobacterium (blue-green alga) microcystis viridis

Abstract A toxin, named as cyanoviridin RR ( 1 ), has been isolated from the cyanobacterium Microcystis viridis . The structure of the toxin has been determined by modern NMR techniques such as the HMBC spectrum.

Anomaly in the modified Mosher's method: Absolute configurations of some marine cembranolides

Abstract Utility of the modified Moshers method is examined by applying it to three marine cembranolides, 2, 3 , and 4 , with known absolute configurations, and it is concluded that the method can be safely used for the, compounds with a sterically unhindered OH group, but care must be taken in applying it to the secondary alcohols with the OH group located in a crowded environment.

Salviolone, a cytotoxic bisnorditerpene with a benzotropolone chromophore from a chinese drug dan-shen (salvia miltiorrhiza)

A new type of bisnorditerpene, salviolone (4) having a benzotropolone moiety has been isolated together with two other nor- and bisnorditerpenes 1 and 2 from the fresh root of Salvia miltiorrhiza. The compounds exhibit cytotoxic activity against Vero cells.

An insight into the conformation of ptilomycalin A. The NMR properties of trifluoroacetylated spermidine analogues

Abstract The conformation of the bis(trifluoroacetyl) derivative of ptilomycalin A (1), a biologically active marine alkaloid, has been deduced from analyzing the NMR properties of the trifluoroacetyl derivatives of spermidine and its analogues.

Acetylsanadaol, a diterpene having a novel skeleton, from the brown alga, Pachydictyon Coriaceum

Abstract Structures of new diterpenoids, sanadol ( 4 ) and acetylsanadol ( 5 ), isolated from Pachydictyon coriaceum , are determined, and sanadaol is produced by an acid-catalyzed ene reaction of dictyodial.

Caryoynencins, potent antibiotics from a plant pathogen pseudomonas caryophylli

Abstract Potent antibiotics, caryoynencins A, B, and C, showing far more remarkable activity than kanamycin A have been isolated from the liquid culture of a plant pathogen Pseudomonas caryophylli.