Enantioselective synthesis of (+)-penostatin E.

The first enantioselective total synthesis of penostatin E has been accomplished. Two highly efficient and diastereoselective reactions, a Hosomi-Sakurai allylation and an intramolecular Pauson-Khand reaction, were utilized for the construction of the basic carbon framework of the target molecule as the key steps. A late-stage introduction of the side chain and a successful base-promoted elimination reaction afforded an efficient synthetic route to (+)-penostatin E.

Regiocontrolled construction of furo[3,2-c]pyran-4-one derivatives by palladium-catalyzed cyclization of propargylic carbonates with 4-hydroxy-2-pyrones.

The reaction of propargylic carbonates with 4-hydroxy-2-pyrones in the presence of a palladium catalyst is described. By the choice of the reaction temperature, two types of the substituted furo[3,2-c]pyran-4-one derivatives were regioselectively synthesized, respectively.

Stereocontrolled total synthesis of natural products with characteristic molecular structures and biological activities.

Total synthetic studies on natural products with promising biological profiles, coupled with their intriguing structural features, are described. The target molecules dealt with in this article are five helianane-type sesquiterpenes (heliannuols A, D and K and heliespirones A and C) and three meroterpenes (breviones A, B and C) with allelopathic activity, as well as four cytotoxic polyketides (lasonolide A and aspergillides A, B and C) and two pyrrolidinoindoline alkaloids (physostigmine and psychotrimine) with acetylcholine esterase inhibitory and antibacterial activities.

Synthesis of oxazolidinones by efficient fixation of atmospheric CO2 with propargylic amines by using a silver/1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) Dual-catalyst system.

This'll fix it: efficient fixation of atmospheric CO(2) has been achieved by the reaction of propargylic amines with a silver/DBU dual-catalyst system. Various oxazolidinones were synthesized in moderate to good yields by using substituted propargylic amines.

Total synthesis of debromoflustramines B and E based on the intramolecular carbamoylketene-alkene [2 + 2] cycloaddition.

Total synthesis of debromoflustramines B and E has been accomplished by using a platinum-catalyzed addition reaction of o-aminophenylboronic acid with the allene and an intramolecular carbamoylketene-alkene [2 + 2] cycloaddition for the construction of the basic carbon framework of the target alkaloids as the key steps.

Total synthesis of natural enantiomers of heliespirones A and C via the diastereoselective intramolecular Hosomi-Sakurai reaction.

A full account of the development of a novel type of the intramolecular Hosomi-Sakurai reactions of the substrates with a p-benzoquinone and an allylsilane moieties connected by an ether linkage is described. This transformation proceeds via an addition-elimination sequence and provides the products with two stereogenic centers through a 1,3(or 1,4)-asymmetric induction in good to excellent diastereoselectivities. A reasonable mechanistic possibility for the reaction, determination of the stereochemistry for the product, and scope and limitation of the transformation are also discussed. The methodology developed here can successfully be applied to the enantiocontrolled total synthesis of the natural enantiomers of (-)-heliespirone A and (+)-heliespirone C, which have been isolated from sunflower Helianthus annuus L. as allelochemicals.

Enantioselective synthesis of 8-epi-xanthatin and biological evaluation of xanthanolides and their derivatives.

An enantioselective synthesis of 8-epi-xanthatin (9) has been accomplished starting from the bicyclic lactone 3, which has been used for the synthesis of other xanthanolides, sundiversifolide (4) and diversifolide (5), through a synthetic route without the use of a selenium species. Additionally we have evaluated antimicrobial activities of five natural xanthanolides and their derivatives. Although the synthetic xanthanolides did not show any activity against methicillin-resistant Staphylococcus aureus (MRSA), some of the synthetic intermediates did exhibit moderate antimicrobial activities.

Enantiocontrolled total syntheses of breviones A, B, and C.

Enantiocontrolled total syntheses of the breviones A, B, and C have been accomplished using a highly diastereoselective oxidative coupling of an α-pyrone with a tricyclic diene prepared from an optically pure Wieland-Miescher ketone derivative through the 7-endo-trig mode of acyl radical cyclization.

S-15176 and its methylated derivative suppress the CsA-insensitive mitochondrial permeability transition and subsequent cytochrome c release induced by silver ion, and show weak protonophoric activity.

A recent report has described that S-15176 (N-[(3,5-di-tert-butyl-4-hydroxy-1-thiophenyl)]-3-propyl-N'-(2,3,4-trimethoxybenzyl) piperazine), an anti-ischemic agent, inhibits the mitochondrial permeability transition (PT) induced by not only Ca(2+) and inorganic phosphate, but also by tert-butylhydroperoxide or phenylarsine oxide [Morin et al. (Biochem Pharmacol 72:911-918, 2006)]. In the present study, we tested the effects of S-15176 on the PT induced by Ag(+), PT of which is not suppressed by cyclosporin A or oligomycin. S-15176 was effective in suppressing the PT and the subsequent cytochrome c release induced by Ag(+), and hence, it was concluded to be a more universal PT inhibitor than cyclosporin A or oligomycin. In addition to the PT-suppression activity, S-15176 also showed weak protonophoric activity. Thus, we further tested to investigate whether the hydroxyl group of S-15176 was involved in its PT-suppression or weak protonophoric activities. The methylated derivative of S-15176 also showed both PT suppression and weak protonophoric activities; hence, the hydroxyl group of S-15176 was concluded not to be involved in these activities.

Synthesis of substituted 1,4,5,6-tetrahydrocyclopenta[b]pyrroles by platinum-catalyzed cascade cyclization/ring expansion of 2-alkynyl-1-azaspiro[2.3]hexanes.

The reaction of 2-alkynyl-1-azaspiro[2.3]hexanes with a platinum catalyst is described. 1,4,5,6-Tetrahydrocyclopenta[b]pyrroles having a variety of substituents were conveniently synthesized via a cascade cyclization/ring-expansion process.