Akio Furusaki

X-Ray crystal structure of staurosporine: a new alkaloid from a Streptomyces strain

The structure of staurosporine (1), a new alkaloid from a Streptomyces strain, has been established by X-ray crystallography.

Glycinoeclepin A, a natural hatching stimulus for the soybean cyst nematode

A large-scale of isolation of glycinoeclepin A, a natural hatching stimulus for the soybean cyst nematode, and its structure elucidation by spectroscopic and X-ray methods are described.

X-Ray crystal structure of herquline, a new biologically active piperazine from Penicillium herquei Fg-372

Herquline, a biologically active subtance from P. herquei, has been shown by X-ray analysis to have the structure (1).

Photo-induced transformations. Part 51. Photo- and thermally-induced rearrangements of hypoiodites of steroidal homoallyl alcohols. The formation of some oxygen heterocycles via photo- and thermally-induced rearrangements of 3-hydroxy-Δ5-steroid hypoiodites in the presence of mercury(II) oxide and iodine

Hypoiodites of cholesterol and epicholesterol in benzene containing mercury(II) oxide and iodine underwent photo-induced rearrangement to give 3α,5-epoxy-6β- and -6α-iodo-A-homo-4-oxa-5α-cholestanes (3) and (4), together with 3-formyloxy-2-iodo-A-nor-2,3-secocholest-5-ene (2). Stereochemistry of the epoxide (3) was established by an X-ray crystallographic analysis. When the reaction of cholesterol hypoiodite was induced thermally at 55–60 °C, only the 6β-isomer, accompanied by cholest-5-en-3α-yl A-homo-4-oxacholest-5-en-3α-yl ether (20) and A-homo-4-oxacholest-5-en-3α-ol (21), is formed. Catalytic hydrogenolysis of iodo-epoxide (3) or (4) gave 3α,5-epoxy-A-homo-4-oxa-5β-cholestane (16) which was transformed into 2-acetyl-5-acetoxymethyl-4-oxa-5β-cholest-2-ene (29) upon treatment with boron trifluoride–ether–acetic anhydride in benzene.In contrast, the newly synthesized hypoiodite of 3α,4,4-trimethylcholest-5-en-3β-ol, in benzene containing mercury(II) oxide and iodine, gave 2-acetyl-3-oxacholest-5-enes (26) and (27) together with 3α,5α-epoxy-A-homo-4-oxasteroids (24) and (25) on irradiation or thermolysis. The formation of the products (26) and (27) indicates the intervention of a common oxyl radical (E) in the rearrangements of 3-hydroxy-Δ5-steroid hypoiodites to products (3), (4), (24), (25), (26), and (27). The pathways of the rearrangements and the stereoselectivity of the reactions are discussed.

Control of axial–equatorial interactions in (dimethylglyoximato)cobalt(III) complexes. Part 1. Counter cation effect on the strength of the intermolecular hydrogen bond, OH ⋯ O–, of trans-bis(dimethylglyoximato)dinitrocobaltate(III) anions and crystal structure of the tetramethylammonium salt

The infrared frequencies observed for the particular functional group of both the axial and the equatorial ligands of the complex anion [Co(Hdmg)2(NO2)2](H2dmg = dimethylglyoxime) have been found to be widely different upon changing the counter cations M+(M = Li, Na, K, Rb or Cs) or NR4+(R = H, Me, Et or Bu). In particular, the O–H stretching frequency of the intramolecular hydrogen bond, O–H ⋯ O–, changes markedly depending on the kind of counter cation. Alkali-metal counter cations, M+, would exert a co-ordination effect upon the donor atom in the complex anion, while tetraalkylammonium counter cations would give a predominantly long-range potential effect only. In order to investigate the difference in the counter cation effects on the strength of the in-plane intramolecular hydrogen bond, crystal and the molecular structures of [NMe4][Co(Hdmg)2(NO2)2] and Na[Co(Hdmg)2(NO2)2]·2H2O were compared. An unusual conformation around the Co–NO–2 moiety was observed in [NMe4][Co(Hdmg)2(NO2)2]. The orientation of the axial ligands, NO2–, is restricted in such a way that they are located over the five-membered chelate ring formed by the Hdmg– moiety and the CoIII atom. On the other hand, Na[Co(Hdmg)2(NO2)2]·2H2O has a usual conformation which would lead to minimum non-bonded interaction between the Hdmg– moietry and the two axial ligands, NO2–. In this conformation, two NO2– are positioned over the pseudo-six-membered chelate rings. A further important structural feature in [NMe4][Co(Hdmg)2(NO2)2] is a very long Co–NO–2 distance [1.974(3), as compared with 1.949(3) and 1.943(3)A in the sodium salt]. This difference is ascribed to the counter cation effect. The stretching frequencies of O–H ⋯ O– and CN in [NMe4][Co(Hdmg)2(NO2)2] are quite different from those in Na[Co(Hdmg)2(NO2)2]·2H2O. These facts suggest that the counter cations play an important role in controlling the axial–equatorial interactions in [Co(Hdmg)2(NO2)2]–.

A new stereospecific rearrangement of an excited steroidal α,β-unsaturated cyclic ketone oxime

Irradiation of (E)-5α-cholest-1-en-3-one oxime in protic or aprotic solvent with a low pressure mercury arc gave 4α′,5-dihydro-A-nor-5α-cholestano[2,1-c]isoxazole, the molecular structure of which was established by X-ray analysis, and a mechanism, which accommodates in stereospecificity of this new photo-rearrngement proved by deuterium labelling studies, is suggested.

X-Ray crystal and molecular structure and the circular dichroism of 2-aza-A-homo-5α-cholestan-1-one

2-Aza-A-homo-5α-cholestan-1-one (2), which exhibits and n→π* c.d. Cotton effect with the sign opposite to that predicted by Oguras sign rule, is shown by X-ray diffraction to contain a quasi-chair seven-membered lactam ring with a mean C-7–NH–CO–C-3 dihedral angle of –20° indicating that the ‘amide’ chromophore is twisted in a way which is opposite to that of caprolactam (1).

Solanascone: a novel sesquiterpene ketone from Nicotiana tabacum. X-Ray structure determination of the corresponding oxime

Solanascone (1), a new tetracyclic sesquiterpene ketone, has been isolated from Nicotiana tabacum cv. Burley; its structure was confirmed by X-ray analysis of its corresponding oxime (2).