Red-Light-Promoted Radical Cascade Reaction to Access Tetralins and Dialins Enabled by Zinc(II)porphyrin, A Light-Flexible Catalyst.

[5,15-Bis(pentafluorophenyl)-10,20-diphenylporphinato]zinc(II) (1), a metalloporphyrin derivative that was recently reported as an efficient photocatalyst driven by blue LEDs by our group, was found to catalyze a red-light-promoted (630 nm LEDs) radical cascade reaction of N-3-arylpropionyloxyphthalimides with radicophiles including electron-deficient alkenes and alkynes, providing access to a range of functionalized tetralin and dialin derivatives. The radical cascade reaction catalyzed by 1 took place via an oxidative quenching cycle in DMSO, where no sacrificial electron donor was required, uncovering a unique solvent effect capable of promoting the porphyrin catalysis.

Radical-Based Route to Functionalized Tetralin: Formal Total Synthesis of (±)-Hamigeran B.

A formal synthetic route to hamigeran B, an antiviral marine natural product with a unique tricyclic molecular architecture, has been developed. The key chemical transformations in the present route include a novel zinc(II)porphyrin-catalyzed photoredox radical cascade cyclization to access a functionalized tetralin, a catalyst-free benzylic radical bromination with NBS by visible-light irradiation, and a samarium(II)-induced cyclization of brominated tetralone possibly via an orthoquinodimethane-like intermediate.

Inhibition of BACE1 and Amyloid-ß Aggregation by Meroterpenoids from the Mushroom Albatrellus yasudae.

To develop drugs to treat Alzheimer's disease (AD) on the basis of the amyloid cascade hypothesis, the amyloid-ß (Aß) aggregation inhibitory activities of 110 extracts from mushrooms were evaluated by thioflavin T (Th-T) assays. The MeOH extract of Albatrellus yasudae inhibited Aß aggregation, and the bioactivity-guided fractionation of the extract afforded four novel meroterpenoids, named scutigeric acid (1), albatrelactone methyl ester (2), albatrelactone (3), and 10',11'-dihydroxygrifolic acid (4), together with two known compounds, grifolin (5) and grifolic acid (6). The structures of 1-4 were elucidated using NMR, MS, UV, IR, and induced ECD spectral data. The structure of 1 was determined as a methyl ester (1a) by 2D NMR spectroscopy. Th-T assays showed that compounds 1-4 and 1a possessed inhibitory activities against Aß aggregation, with IC50 values of 6.6, 40.7, 51.4, 53.3, and 50.3 µM, respectively. Notably, 1 possessed an inhibitory activity against Aß aggregation comparable to that of myricetin as a positive control. Moreover, 1-6 exhibited inhibitory activities against BACE1, with IC50 values of 1.6, 10.9, 10.5, 34.4, 6.1, and 1.4 µM, respectively.

Proton-accelerated Lewis acid catalysis for stereo- and regioselective isomerization of epoxides to allylic alcohols.

The isomerization of epoxides to allylic alcohols was developed via proton-accelerated Lewis acid catalysis. The addition of tBuOH as a proton source is the key to the efficient catalytic cycle. Trisubstituted epoxides, including enantioenriched derivatives, were selectively converted to secondary-allylic alcohols without loss of enantiopurity.

Central zinc metal-controlled regioselective meso-bromination of zincatedß-silylporphyrins-rapid access to meso,ß-dual-functionalized porphyrins.

A convenient method for the preparation of meso,ß-dual-functionalized porphyrin was developed. The bromination of zincatedß-silylporphyrin with NBS selectively yielded meso-bromo-ß-silylporphyrin, whereas, the bromination of free-baseß-silylporphyrin selectively yielded ß-bromoporphyrin via an ipso-substitution of the silyl group. These meso,ß-dual-functionalized porphyrins could be used as multipurpose synthons for fabricating various porphyrin derivatives.

Chiroptical Protocol for the Absolute Configurational Assignment of Alkyl-Substituted Epoxides Using Bis(zinc porphyrin) as a CD-Sensitive Bidentate Host.

The absolute configurations of simple alkyl-substituted chiral epoxides not bearing other ligating groups are readily determined via the exciton-coupled circular dichroism (ECCD) protocol using bidentate bis(zinc porphyrin) host system BP1 as a CD-sensitive chirality probe. In this situation, chiral epoxides can successfully be incorporated into the cleft of V-shaped host BP1 by double coordination of both oxygen lone pairs of the guest to the two central zinc ions of the host. We also propose a working model based on an MM2 optimized structure of the substrates that enables nonempirical prediction of the chirality of the bound epoxide.

Regioselective ß-silylation of porphyrins via iridium-catalyzed C-H bond activation.

An efficient approach to meso-unsubstituted ß-silylporphyrins was developed through highly regioselective Ir-catalyzed C-H activation, in the presence of HSiMe(OSiMe3)2 as the Si source, from meso-unsubstituted porphyrins. Further transformations of the silyl group, such as oxidation, halogenation, and cross-coupling reactions, could be achieved under mild conditions, demonstrating the synthetic utility of ß-silylporphyrins as a multipurpose synthon for fabricating porphyrin derivatives.

Bis(zinc porphyrin) as a CD-sensitive bidentate host molecule: direct determination of absolute configuration of mono-alcohols.

A facile and direct protocol to determine the absolute configurations of chiral mono-alcohols without analyte derivatization can now be realized using a novel circular dichroic (CD)-sensitive bis(zinc porphyrin) BP1 host system. The binding of mono-alcohols to BP1 should be greatly enhanced by the simultaneous double coordination of the hydroxyl group to the two central metals of the porphyrin subunits.

Palladium-catalyzed Kumada coupling reaction of bromoporphyrins with silylmethyl Grignard reagents: preparation of silylmethyl-substituted porphyrins as a multipurpose synthon for fabrication of porphyrin systems.

We have developed an efficient method for preparing silylmethyl-substituted porphyrins via the palladium-catalyzed Kumada cross-coupling reaction of bromoporphyrins with silylmethyl Grignard reagents. We demonstrated the synthetic utility of these silylmethylporphyrins as a multipurpose synthon for fabricating porphyrin derivatives through a variety of transformations of the silylmethyl groups, including the DDQ-promoted oxidative conversion to CHO, CH(2)OH, CH(2)OMe, and CH(2)F functionalities and the fluoride ion-mediated desilylative introduction of carbon-carbon single and double bonds.

Metallophthalocyanine complex, Cr(TBPC)OTf: an efficient, recyclable Lewis acid catalyst in the regio- and stereoselective rearrangement of epoxides to aldehydes.

The metallophthalocyanine complex Cr(TBPC)OTf works as a highly efficient, recyclable Lewis acid catalyst for the regio- and stereoselective rearrangements of epoxides to aldehydes.

An efficient one-pot procedure for asymmetric bifunctionalization of 5,15-disubstituted porphyrins: a simple preparation of meso acyl-, alkoxycarbonyl-, and carbamoyl-substituted meso-formylporphyrins.

An efficient one-pot procedure which converts 5,15-disubstituted porphyrins into their corresponding meso acyl-, alkoxycarbonyl-, and carbamoyl-substituted meso-formylporphyrins has been developed, where the procedure involves a sequential S(N)Ar reaction of porphyrins with PyMe(2)SiCH(2)Li, followed by acylation or related reactions and oxidation.

One-pot synthesis of meso-formylporphyrins by S(N)Ar reaction of 5,15-disubstituted porphyrins with (2-pyridyldimethylsilyl)methyllithium.

A simple, one-pot procedure that converts 5,15-substituted porphyrins into the corresponding meso-formylated porphyrins has been developed. The method, based on a new synthetic concept for functionalized porphyrins utilizing the (2-pyridyldimethylsilyl)methyl group as a latent formyl functionality, affords the desired product in good yield and is especially appropriate for the direct formylation of free base porphyrins, which has never been achieved by known methods.

Palladium-catalyzed cyanation of porphyrins utilizing cyanoethylzinc bromide as an efficient cyanide ion source.

Palladium-catalyzed cyanation of bromoporphyrins is now realized using cyanoethylzinc bromide as a specific cyanating agent. This new protocol provides an easy access to various cyanated Zn(II) porphyrins, including meso-mono-, meso-di-, and beta-mono-cyano-substituted Zn(II) complexes. [reaction: see text]

Highly regio- and stereoselective rearrangement of epoxides to aldehydes catalyzed by high-valent metalloporphyrin complex, Cr(TPP)OTf.

Chromium(III) tetraphenylporphyrin triflate, Cr(TPP)OTf, works as an efficient and characteristic Lewis acid catalyst in the regio- and stereoselective rearrangement of epoxides to aldehydes. This Cr(TPP)OTf-catalyzed reaction is an operationally simple and especially convenient method for synthesizing optically active beta-siloxy aldehydes from 2,3-epoxy silyl ethers which are readily available in enantiomerically enriched forms by the Sharpless epoxidation of allylic alcohols followed by silylation.