Tetsuro Shinada

Structure Determination of a New Juvenile Hormone from a Heteropteran Insect

The structure of the juvenile hormone (JH) in the suborder Heteroptera, order Hemiptera, has been known for a very long time to be different from the JH of other orders, but the structure has been a matter of controversy. The structure was first elucidated by an unprecedented approach involving the screening of a JH molecular library. The novel Heteroptera-specific JH (JHSB3) is a new category of JH that is featured by the skipped bisepoxide structure.

An efficient synthesis of α-acyloxyketone by Cu(acac)2-catalyzed insertion reaction of α-diazoketone to carboxylic acid

Abstract An efficient insertion reaction of α-diazoketone to various carboxylic acids was achieved by using Cu(acac) 2 as a catalyst. Treatment of the diazo compound with a carboxylic acid (1.2 equiv) in the presence of Cu(acac) 2 (0.1 equiv) at room temperature afforded the corresponding ketoester in good yield. Various kinds of functional groups were tolerated under the reaction conditions.

An Unusual Terpene Cyclization Mechanism Involving a Carbon–Carbon Bond Rearrangement

Terpene cyclization reactions are fascinating owing to the precise control of connectivity and stereochemistry during the catalytic process. Cyclooctat-9-en-7-ol synthase (CotB2) synthesizes an unusual 5-8-5 fused-ring structure with six chiral centers from the universal diterpene precursor, the achiral C20 geranylgeranyl diphosphate substrate. An unusual new mechanism for the exquisite CotB2-catalyzed cyclization that involves a carbon-carbon backbone rearrangement and three long-range hydride shifts is proposed, based on a powerful combination of in vivo studies using uniformly (13)C-labeled glucose and in vitro reactions of regiospecifically deuterium-substituted geranylgeranyl diphosphate substrates. This study shows that CotB2 elegantly demonstrates the synthetic virtuosity and stereochemical control that evolution has conferred on terpene synthases.

Indium mediated Barbier-type allylation of aldimines in alcoholic solvents

Abstract Barbier-type allylation of unactivated aldimines with allyl bromides in the presence of indium powder took place rapidly in alcoholic solvents to give homoallylic amines in fair to good yields.

A facile method for the conversion of oximes to ketones and aldehydes by the use of activated MnO2

Abstract Activated manganese dioxide (MnO 2 ) was found to be an efficient oxidant in the conversion of oximes to carbonyl compounds. The utility of this method in synthesis was demonstrated by the conversion of galactose to its acyclic aldose derivative 5.

Using Stable Radicals To Protect Pentacene Derivatives from Photodegradation

Organic transistors and organic devices have a variety of applications in molecular electronics and in the up-andcoming area of organic molecular spintronics. The use of inexpensive and facile ink-jet methods is possible for the fabrication of organic semiconductors. Pentacene and its derivatives 7] have attracted increasing interest as promising electronic materials owing to their high hole mobility. Pentacene is the most promising candidate for organic fieldeffect transistor (OFET) applications. However, its chemical instability in the presence of light and air prevents practical applications. Efforts have been made to improve the stability by the addition of substituents. 7] The most notable example is 6,13-bis(triisopropylsilylethynyl)pentacene, 10] in which the 6and 13-positions of pentacene are protected by triisopropylsilylethynyl groups. For this pentacene derivative, extremely high hole mobility of 1.8 cm V 1 s 1 was reported for the thin film. However, the addition of substituents to photoactive carbon sites prevents further functional modifications because both the 6and 13-positions are blocked by the substituents and also the characteristic nature of the pentacene moiety is changed. Herein, we report a new method that utilizes a stable radical to protect pentacene derivatives from photodegradation. During the course of our systematic studies of pconjugated spin systems with high-spin photo-excited states for functional materials, we have discovered that a combination of two unstable species (photoreactive pentacene and a radical) leads to remarkable protection from photodegradation and an enhancement in solubility in common organic solvents. These effects are advantageous for practical applications of acene derivatives in molecular electronic devices. Radicals are well-known energy scavengers of the photoexcited state. We have utilized this characteristic of radicals to scavenge the energy of the photoexcited state of pentacene. Two novel radical pentacene hybrids, Pen–Ph–OV (1a) and Pen–Ph–NN (2a) and their precursors (1 b and 2b) were synthesized (Scheme 1; Pen, Ph, OV, and NN denote pentacene, phenyl, oxo-verdazyl radical, and nitronyl nitroxide radical moieties, respectively). We demonstrate the remarkable photochemical stability induced by the attachment of

Oxidation of hydrazones by hypervalent organoiodine reagents: Regeneration of the carbonyl group and facile syntheses of α-acetoxy and α-alkoxy azo compounds

Abstract Various hydrazone derivatives of α-keto esters were prepared. The carbonyl group was readily regenerated in high yield from phenylhydrazones through oxidative hydrolysis using hypervalent organoiodine(III) reagents—either bis(trifluoroacetoxy)-iodobenzene (BTIB) in aqueous acetonitrile or hydroxy(tosyloxy)iodobenzene (HTIB) in chloroform. α-Acetoxy phenyl- or methylazo compounds were readily synthesized by oxidation of the corresponding hydrazones with iodobenzene diacetate (IBDA) in dichloromethane or acetic acid. α-Methoxy phenyl- or methylazo compounds were also prepared by oxidation of the hydrazones in methanol. The mechanisms of the oxidation reactions are discussed.

Novel mastoparan and protonectin analogs isolated from a solitary wasp, Orancistrocerus drewseni drewseni

Two novel biologically active peptides, Eumenine mastoparan-OD and Orancis-Protonectin, were isolated from a solitary wasp, Orancistrocerus drewsenidrewseni (Eumeninae, Vespidae). MALDI-TOF MS analysis of a small amount of the crude venom gave two intensive molecular-related ion peaks at m/z 1269.9 and 1552.9 that were expected to be novel based on a peptide database search. Purification of the crude venom by HPLC gave two peptide fractions, P-1 and P-2. The amino acid sequence of P-1 (GRILSFIKAGLAEHL-NH2) and P-2 (ILGIITSLLKSL-NH2) were determined by ESI-MS/MS, automated Edman degradation, and amino acid analysis. According to the high sequence homology with those of mastoparan and protonectin, P-1 and P-2 were labeled Eumenine mastoparan-OD and Orancis-Protonectin, respectively. Orancis-Protonectin is the first example of a protonectin analog isolated from the venom of a solitary wasp. The hemolytic activities of these new peptides were more potent than that of mastoparan.

Novel and efficient transformation of α-amino nitrile to α-imino and α-amide nitriles in asymmetric Strecker synthesis

Abstract Oxidation of α-amino nitrile 4 with ozone gave rise to a mixture of α-imino nitrile 5 and a novel fragmentation product of 6 in one-step. The mixture was converted to a variety of α-substituted α-amino acids 7 in high yields, which enabled the asymmetric transferring Strecker synthesis to be a widely useful method.

Facile synthesis of 6-hydroxyindole-3-acetic acid: On the structure of the aromatic subunit of nephilatoxin-1∼6

Abstract A facile synthesis of 6-hydroxyindole-3-acetic acid 1a, which is the proposed aromatic subunit of NPTX-1∼6, is described. Radical cyclization of isonitrile 2 successfully afforded 9 in high yield. The aromatic subunit of NPTX-1∼6 was confirmed as 4-hydroxyindole-3-acetic acid 12 by comparison of the 1H-NMR spectra with those of authentic 4- and 6-hydroxyindole-3-acetic acids.