Masao Arimoto

Reaction of alkynyltrimethylsilanes with a hypervalent organoiodine compound: A new general synthesis of alkynyliodonium salts

Abstract New general methods for the synthesis of alkynyl(phenyl)iodonium tetrafluoroborate 2 from alkynyltrimethylsilanes 1 utilizing the combination of iodosylbenzene and triethyloxonium tetrafluoroborate or boron trifluoride etherate were developed. The medium effect observed in the reaction was also discussed.

Iodosylbenzene-trimethylsilyl azide-boron trifluoride etherate: A highly efficient system for direct synthesis of allyl azides from allylsilanes

Abstract Simple method for the synthesis of allyl azides from allyltrimethylsilanes utilizing the combination of iodosylbenzene-trimethylsilyl azide-boron trifluoride etherate in dichloromethane was developed. A reaction mechanism involving the allyliodine(III) species was proposed.

Facile and efficient synthesis of naturally occurring carbasugars (+)-pericosines A and C.

An efficient synthesis of antitumor marine natural product (+)-pericosine A was achieved from (-)-quinic acid in 11.7% overall yield, which is 20 times better than our previously reported synthesis. The crucial steps of this synthesis include the regio- and stereoselective bromohydrination of an unstable diene and the ring opening of an epoxide. This synthetic route was applicable to a synthesis of (+)-pericosine C and also to a synthesis of (-)-pericosine C.

Oxidation of 2-substituted allylsilane to conjugated enal using hypervalent organoiodine compound and synthesis of α-methylen γ-and δ-lactones

Abstract 2-Substituted allylsilanes 1 on treatment with iodosbenzene and boron trifluoride etherate in dioxane afforded conjugated enals 2 directly in good yield, from which α-methylen γ- and δ-lactones 7 were synthesized.

Design and synthesis of regioisomerically pure unsymmetrical xanthene derivatives for staining live cells and their photochemical properties

We have demonstrated the synthesis of regioisomerically pure unsymmetrical xanthene derivatives consisting of three units which can be independently modified to control their physical properties. The photochemical properties of the synthetic unsymmetrical xanthene derivatives were investigated in solution by UV-vis absorption and fluorescence measurements, and their cell imaging properties were examined by confocal laser-scanning microscopy.

Effects of amino acids and chirality for molecular folding of desoxazoline‐ascidiacyclamide derivatives: X‐ray crystal structures of four cyclic octapeptides including unusual amino acids, cyclo(–Ile–aThr–D‐Val–Thz–)2, cyclo(–Ala–aThr–D‐Val–Thz–Ile–aThr–D‐Val–Thz–), cyclo(–Val–aThr–D‐Val–Thz–Ile–aThr–D‐Val–Thz–), and cyclo(–Ile–aThr–Val–Thz–Ile–aThr–D‐Val–Thz–)

Desoxazoline derivative of ascidiacyclamide (1), cyclo(-L-Ile-L-allo-threonine-D-Val-thiazole-)(2), was modified to disturb the C(2)-symmetry. An Ile(1) residue of 1 was replaced for Ala (2) or Val (3), and the D-Val(3) residue was replaced for Val (4). The crystal structures of 1-4 were analyzed by x-ray diffraction methods. The molecules of all compounds were folded and this type of structure was not observed in x-ray structures of ascidiacyclamide derivatives so far except for patellamide D. The folding patterns of 1-4 were similar to each other and resembled that of patellamide. The asymmetric modifications at position 1 caused the conformational changes at local area, and these were related with the peptide-peptide and peptide-solvent interactions. Despite the diverse backbone conformation by the epimeric modification at position 3, the entire molecule of 4 was folded. These results mean that (1) the desoxazoline-ascidiacyclamides favored the folded structures and (2) the modifications of the side chain size at position 1 and the chirality at position 3 brought the local conformational changes to derivatives, suggesting that (3) the lack of the oxazoline block leads to conformational flexibility of 1-4, which accepts the conformational change with no drastic change on the entire structure.

Synthesis of 4-aryl-1H-pyrazoles by Suzuki-Miyaura cross coupling reaction between 4-bromo-1H-1-tritylpyrazole and arylboronic acids

A general procedure for the synthesis of 4-aryl-1H-pyrazoles by the Suzuki-Miyaura cross coupling reaction between 4-bromo-1H-1-tritylpyrazole and commercially available arylboronic acids was developed. Using this procedure, a direct synthesis of 4-aryl-1H-pyrazoles possessing functional groups, such as hydroxyl, nitro, and amino groups, on the aryl ring was realized. Those molecules could not be prepared by our previous synthesis of 4-aryl-1H-pyrazoles via the Kumada cross coupling reaction.

Inhibitory Activity of Podophyllotoxin and Matairesinol-derivative Lignans on the Root Growth of Brassica campestris

All the lignans tested in a bioassay with Brassica campestris L. subsp. rapa Hook. fil. et Anders inhibited the root growth of this plant, except for deoxypicropodophyllin. The effects of functional groups in the molecule on the inhibitory activity of these compounds were studied. It is suggested that the methylenedioxyl group and the stereochemical configuration of the lactone junction of podophyllotoxin derivatives were closely related to the inhibitory activity. The O-methyl derivative of two hydroxyl groups of matairesinol greatly enhanced the inhibition of root growth in this plant.

Hypervalent organoiodine chemistry: a new synthesis of β-methylene cyclic ethers

The allylsilanes (1), containing suitably-substituted hydroxy-groups, on treatment with iodosylbenzene in the presence of BF3–Et2O in an ether solvent, give 5- or 6-membered β-methylene cyclic ehters (3) in good yields, presumably via the highly reactive alylaryliodonium intermediates (2).

Synthesis of aryltetralin type 2-azalignans using Schollkopf's bislactim-ether methodology

Synthesis of (1S,3R)-2-aza-4-deoxypodophyllotoxin has been accomplished in 6 steps using Schollkopfs bislactim-ether methodology in 12% total yield. Bislactim-ether, which was originally prepared from commercially available L -valine and glycine, was used as the starting material. Our synthetic route was allied to easy access to aryltetralin type 2-azalignan analogues. Synthesized 2-azalignans were tested for in vitro anticancer activity using a panel of human cancer cell lines. Both of two (1S)-diastereomers (9a and 9b) of 2-aza-4-deoxypodophyllotoxin showed significant activity against human cancer cell lines: A-549 (lung), HTC-8 (ileocecal), and MCF-7 (breast cancer).