Search

The first example of photoredox strategy for synthesis of phenanthrene skeletons through C(sp3)-H functionalization under external oxidant-free conditions is achieved. This transformation relies on the keto-enol tautomerism of 1,3 dicarbonyl moiety, i.e., the enol form of 1,3-dicarbonyl derivatives with relatively lower oxidation potential can be activated by the excited acridinium photocatalyst. The electron and proton eliminated from the substrate are immediately captured by a cobaloxime catalyst to exclusively afford a-carbonyl radical for highly substituted 10-phenanthrenols in good to excellent yields.

A pair of enantiomeric norsesquiterpenoids, (+)- and (−)-preuisolactone A (1) [(+)-1 and (−)-1)] featuring an unprecedented tricyclo[4.4.01,6.02,8]decane carbon scaffold were isolated from Preussia isomera. Their structures were determined by spectroscopic and computed methods and X-ray crystallography. Compounds (+)-1 and (−)-1 are two rare naturally occurring sesquiterpenoidal enantiomers. A plausible biosynthetic pathway for 1 is proposed. Additionally, (±)-1 exhibited remarkable antibacterial activity against Micrococcus luteus with an MIC value of 10.2 μM.

The first example of photoredox strategy for synthesis of phenanthrene skeletons through C(sp

Genome mining of an indolocarbazole-type gene cluster from a marine-derived Nocardiopsis flavescens NA01583 strain led to the discovery of three new indolocarbazole alkaloids (1-3). Heterologous expression of the intact loo gene cluster in a surrogate host Streptomyces lividans K4-114 led to the successful production of 3. Notably, compound 1 showed potent cytotoxic activities toward eight cancer cell lines with IC50 values ranging from 41 to 283 nM.

A rare fungal hopane-type triterpenoid glycoside fumihopaside A was identified by genome mining in combination with HPLC–MS/MS in Aspergillus fumigatus. Combining genetic deletions in A. fumigatus with heterologous reconstitutions in Aspergillus nidulans of the afum gene cluster, we identified one fungal squalene hopane cyclase AfumA charging the cyclization of the hopene skeleton, one cytochrome P450, and one UDP-glycosyltransferase. Bioassays indicated that fumihopaside A plays important roles in protecting A. fumigatus against heat or ultraviolet stress.

A pair of enantiomeric norsesquiterpenoids, (+)- and (-)-preuisolactone A (1) [(+)-1 and (-)-1)] featuring an unprecedented tricyclo[4.4.0

A novel, facile, and efficient method for the synthesis of tetrahydropyridazines by a one-pot tandem reaction of easily accessible ketohydrazones and olefins in the presence of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) has been successfully developed. The reaction involves the initial generation of azoalkenes from direct oxidative dehydrogenation of ketohydrazones using TEMPO as the commercially available oxidant, followed by a subsequent aza-Diels-Alder reaction with olefins.

A redox-neutral reaction without using any external oxidant and reductant in one pot is described. By combining a Ru(bpy)32+ photocatalyst and cobaloxime catalyst, a number of tertiary anilines can be oxidized by Ru(bpy)32+ to realize oxidative cyclization of tetrahydroquinolines, and the electron and proton eliminated from the substrate anilines are captured by a cobaloxime catalyst to achieve hydrogen transfer in situ to maleimides, in good to excellent yields, under redox-neutral conditions.

Readily accessible β,γ-unsaturated ketoximes reacted with 2-arylphenylisonitriles under the conditions of t-BuOOH and n-Bu4NI to give isoxazoline functionalized phenanthridines via tandem intramolecular/intermolecular C-O/C-C/C-C bond formation. The reaction involves the initial generation of iminoxyl radicals from the oxidation of β,γ-unsaturated ketoximes by t-BuOOH and n-Bu4NI followed a cascade radical cyclization/addition/cyclization sequence.

The trifluoroethyl aryl ethers are important motifs in drug molecules. However, a report devoted specifically to the study of transition-metal-catalyzed C–H trifluoroethoxylation has not been reported to date. A protocol of Pd(II)-catalyzed o-C–H trifluoroethoxylation of a broad range of benzoic acid derivatives (i.e., N-sulfonylbenzamides) has been developed. This method is also applied to the formal synthesis of the drug molecule flecainide, wherein the first m-C–H trifluoroethoxylation is also exemplified.

An efficient and practical tandem cyclization/addition/cyclization strategy is developed for the initial generated hydrazonyl radicals derived from the oxidation of β,γ-unsaturated hydrazones. By using this protocol, structurally novel pyrazoline-functionalized oxindoles are prepared by the reaction of easily accessible β,γ-unsaturated hydrazones with N-aryl acrylamides under the metal- and solvent-free conditions of DTBP (di-tert-butyl peroxide) via a tandem intra/intermolecular C-N/C-C/C-C bond formation.

Guajadial (1), a novel caryophyllene-based meroterpenoid, was isolated from the Leaves of Psidium guajava (guava). The structure and relative stereochemistry of guajadial (1) were elucidated by extensive spectroscopic analysis. A possible biosynthetic pathway for 1 was proposed.

A novel iminoxyl radical-involved metal-free approach to vicinal oxyoximation and aminooximation of unactivated alkenes is developed. This method utilizes the dichotomous reactivity of the iminoxyl radical to furnish a general difunctionalization on alkenes using simple tert-butyl nitrite (TBN) as the iminoxyl radical initiator as well the carbon radical trap. By using this protocol, oxime featured 4,5-dihydroisoxazoles and cyclic nitrones were facilely prepared from β,γ- and γ,δ-unsaturated ketoximes, respectively.