3,3-Dimethoxypropylsulfonyl Group: A new versatile protecting and activating group for amine synthesis

3,3-Dimethoxypropylsulfonyl (Dimps) chloride was prepared and used as a new versatile sulfonating agent for ammonia, primary and secondary amines to afford corresponding Dimps-amides in excellent yields. The resulting N-nonsubstituted and N-monosubstituted Dimps-amides, activated amines, were alkylated satisfactorily under new Mitsunobu conditions. The Dimps group was removed by treatment in aqueous solution under acidic followed by basic conditions. Furthermore, epilachnene, the defensive droplets from the Mexican bean beetle, Epilachna varivestis, was synthesized utilizing this Dimps methodology in short steps.     

Synthesis and absolute structure of manzacidin B

[reaction: see text] Four possible stereoisomers of manzacidin B were synthesized using stereochemically defined synthetic routes via the azide 7 and oxazoline 11 starting with the (R)-alpha-methyl Garner aldehyde 5. Comparisons of the spectroscopic data of the synthetic isomers 4a-d with those of the natural manzacidin B revised the proposed structure 3 to (4S,5S,6R)-4d.     

Virtually complete E-selective alpha,beta-unsaturated ester synthesis by Hg(OTf)2-catalyzed hydration of sec-ethoxyalkynyl acetate

The reaction of alkyl-substituted sec-ethoxyalkynyl acetates with water catalyzed by Hg(OTf)2 afforded alpha,beta-unsaturated esters in excellent yield with high catalytic turnover up to 1000 times under very mild reaction conditions with virtually complete E-selectivity, superior even to that of the HWE reaction.     

Catalytic activation of the leaving group in the S(N)2 reaction

A novel catalytic activation of the leaving group in the S(N)2 reaction is achieved as an extension of our mercuric triflate-catalyzed reactions. Derivatives of anilinoethyl 4-pentynoate reacted smoothly with catalytic amounts of Hg(OTf)(2) to give indoline derivatives in excellent yield with efficient catalytic turnovers under very mild conditions. The reaction of optically pure secondary alcohol derivatives resulted in inversion of stereochemistry, which is a definitive feature of the S(N)2 reaction. The procedure is applicable for benzoazepine synthesis.     

Toward Palau′amine: Hg(OTf)2‐Catalyzed Synthesis of the Cyclopentane Core

Catalytic cyclization : The Hg(OTf)₂‐catalyzed N‐selective cyclization of amide carbonyl moieties for the construction of a quaternary carbon center was developed. The Hg(OTf)₂‐catalyzed cyclization of cyclopentylidene alcohol with acylhydrazide afforded the desired cyclopenta[c]pyridazinone in good yield. The subsequent eight steps gave the functionalized cyclopentane with the correct stereochemistry that corresponds to the E ring of palau′amine (see scheme).

     

Efficient construction of the hexacyclic ring core of palau'amine: the pKa concept for proceeding with unfavorable equilibrium reactions

Palau''amine has received a great deal of attention as an attractive synthetic target due to its intriguing molecular architecture and significant immunosuppressive activity, and we achieved its total synthesis in 2015. However, the synthesized palau''amine has not been readily applicable to the mechanistic study of immunosuppressive activity, because it requires 45 longest linear steps from a commercially available compound. Here, we report the short-step construction of the ABCDEF hexacyclic ring core of palau''amine. The construction of the CDE tricyclic ring core in a single step is achieved by our pK_a concept for proceeding with unfavorable equilibrium reactions, and a palau''amine analog without the aminomethyl and chloride groups is synthesized in 20 longest linear steps from the same starting material. The palau''amine analog is confirmed to retain the immunosuppressive activity. The present synthetic approach for a palau''amine analog has the potential for use in the development of palau''amine probes for mechanistic elucidation.

A palau''amine analog (2) was synthesized from 2-cyclopentenone in 20 steps. The construction of the CDE tricyclic ring core in a single step is achieved by our pK_a concept for proceeding with the unfavorable equilibrium reactions.     

Precise measurement of positronium hyperfine splitting using the Zeeman effect

Positronium is an ideal system for the research of the quantum electrodynamics (QED) in bound state. The hyperfine splitting (HFS) of positronium, Δ_HFS, gives a good test of the bound state calculations and probes new physics beyond the Standard Model. A new method of QED calculations has revealed the discrepancy by 15 ppm (3.9σ) of Δ_HFS between the QED prediction and the experimental average. There would be possibility of new physics or common systematic uncertainties in the previous all experiments. We describe a new experiment to reduce possible systematic uncertainties and will provide an independent check of the discrepancy. We are now taking data and the current result of Δ_HFS?=?203.395 1 ±0.002 4 (stat., 12 ppm) ±0.001 9 (sys., 9.5 ppm) GHz has been obtained so far. A measurement with a precision of O(ppm) is expected within a year.     

Concise [4+3] cycloaddition reaction of pyrroles leading to tropinone derivatives

A concise [4+3] cycloaddition reaction of pyrroles with 2-(silyloxy)allyl cations has been developed. The oxyallyl cations stabilized with a methylthio group or geminal methyl groups were generated from the corresponding allylic alcohols under the influence of a Brönsted acid (Tf₂NH), respectively. The use of N-nosyl-protected pyrroles as the four-carbon unit was found to give tropinone derivatives in high yield.     

Total synthesis of the (+)-antimycin A3 family: structure elucidation of (+)-antimycin A3a

(+)-Antimycin A_3a (AA_3a), one component of the natural antibiotic antimycin A₃, was synthesized using an asymmetric aza-Claisen rearrangement. The stereochemistry at the 2′ position on the acyloxy side chain of AA_3a was established as S-configuration by comparison of the synthetic AA_3a and the natural AA_3a.     

Wet-chemical etching of Mn-Zn ferrite by focused Ar+-laser irradiation in H3PO4

Maskless etching of Mn-Zn ferrite in H₃PO₄ aqueous solution by Ar⁺-ion laser irradiation has been investigated to obtain high etching rates and aspect-ratios of etched grooves. The etching processes have been found to be photochemical in the low laser power region and thermochemical in the high laser power region. High etching rates of up to 340 μm/s and an aspect-ratio of 30 for slab structures have been achieved. In the case of high aspect-ratio structure, the etching rate was limited by the low diffusion efficiency of etched products in the etchant. Periodic ripple structures have been observed under specific etching conditions.