https://pubs.rsc.org/en/content/articlepdf/2019/NP/C8NP00092A

Marine natural products.

The application of (S)-1,10-binaphthyl-2,20-diol as NMR chiral solvating agent (CSA) for omeprazole, and three of its analogs (lanso-, panto-, and rabe-prazole) was investigated. The formation of diastereomeric host–guest complexes in solution between the CSA and the racemic substrates produced sufficient NMR signal splitting for the determination of enantiomeric excesses by Hor F-NMR spectroscopy. Using of hydrophobic deuterated solvents was mandatory for obtaining good enantiodiscrimination, thus suggesting the importance of intermolecular hydrogen bonds in the stabilization of the complexes. The method was applied to the fast quantification of the enantiomeric purity of in-process samples of S-omeprazole. Chirality 00:000–000, 2009. VC 2009

The assignment of absolute configuration by NMR

The [2 + 2] photocycloaddition is undisputedly the most important and most frequently used photochemical reaction. In this review, it is attempted to cover all recent aspects of [2 + 2] photocycloaddition chemistry with an emphasis on synthetically relevant, regio-, and stereoselective reactions. The review aims to comprehensively discuss relevant work, which was done in the field in the last 20 years (i.e., from 1995 to 2015). Organization of the data follows a subdivision according to mechanism and substrate classes. Cu(I) and PET (photoinduced electron transfer) catalysis are treated separately in sections 2 and 4, whereas the vast majority of photocycloaddition reactions which occur by direct excitation or sensitization are divided within section 3 into individual subsections according to the photochemically excited olefin.

http://pubs.acs.org/doi/pdf/10.1021/acs.chemrev.5b00723

Recent Advances in the Synthesis of Cyclobutanes by Olefin [2+2] Photocycloaddition Reactions

Photochemical reactions contribute in a significant way to the existing repertoire of carbon-carbon bond-forming reactions by allowing access to exceptional molecular structures that cannot be obtained by conventional means. In this Review, the most important photochemical transformations that have been employed in natural product synthesis are presented. Selected total syntheses are discussed as examples, with particular attention given to the photochemical key step and its stereoselectivity. The structural relationship between the photochemically generated molecule and the natural product is shown, and, where necessary, the consecutive reactions in the synthesis are illustrated and classified.

Photochemical reactions as key steps in natural product synthesis

Cyclizations of N-acyliminium ions.

N-Benzyl-α-ethoxycarbonylnitrone (1) was prepared from ethyl glyoxylate and N-benzylhydroxylamine. The reactions of 1 with isobutylene, methyl acrylate, and methyl crotonate are described.

The Preparation of N-Benzyl-α-ethoxycarbonylnitrone and Its Reactions with Some Olefins

Three new bioactive marine diterpenoids, stolonidiol (1), stolonidiol monoacetae (2), and claenone (3), were isolated from Japanese soft coral of the genus Clavularia. The structures of these diterpenoids were elucidated on the basis of spectroscopic data including two-dimensional nuclear magnetic resonance, chemical reactions, and/or X-ray crystallographic analysis. Compounds 1 and 2 showed a strong cytotoxic activity against P388 leukemia cells, and 3 was inhibitory in the fertilized sea urchin egg assay.

Bioactive marine diterpenoids from Japanese soft coral of Clavularia sp.

Stolonidiol, a new marine diterpenoid with a strong cytotoxic activity from the Japanese soft coral

Structures of nine oxygenated 4-methylene sterols from Hachijo marine sponge Theonella swinhoei.

N-Methyl-α-methoxycarbonylmethanimine N-oxide, Z configuration in crystal, was found to exhibit a facile equilibration with its E-isomer in solution. The configuration of N-t-butyl derivative was always Z.

Yoshinobu Inouye

Papers

The Preparation of N-Benzyl-α-ethoxycarbonylnitrone and Its Reactions with Some Olefins

Bioactive marine diterpenoids from Japanese soft coral of Clavularia sp.

Stolonidiol, a new marine diterpenoid with a strong cytotoxic activity from the Japanese soft coral

Structures of nine oxygenated 4-methylene sterols from Hachijo marine sponge Theonella swinhoei.

The Configurations of N-Methyl- and N-t-Butyl-α-methoxycarbonylmethanimine N-Oxides