Activation of Primary C-H Bonds in Oxidative Cyclizations of Tambjamines Catalyzed by Rieske Oxygenases TamC and TamC.

Tambjamines are complex bipyrrole-containing natural products that possess promising bioactive properties. Although is known to produce both cyclic tambjamine MYP1 and the linear precursor (YP1), the biosynthetic machinery used to catalyze the site-selective oxidative carbocyclization at the unactivated 1° carbon of YP1 has remained unclear. Here, we demonstrate that a three-component Rieske system consisting of an oxygenase (TamC) and two redox partner proteins is responsible for this unprecedented activity on YP1 and potentially, a non-native substrate (BE-18591).

New protein tyrosine phosphatase inhibitors from fungus F07ZB1707.

Twelve new compounds, aspergorakhins A-L (1-12) coupled with one known xanthone leptosphaerin D (13), were isolated from the extract of soil-derived fungus F07ZB1707. Their structures were elucidated by spectroscopic data analysis including UV, IR, NMR, and HRESIMS. The absolute configurations of 5 and 8-11 were identified using ECD and OR calculations.

Xylomexicanins K-N: limonoids from the leaves and twigs of .

Six new compounds, xylomexicanins K-N (-), granasteroid () and 5-methoxy-2-pentylbenzofuran-7-ol (), along with nine known compounds were isolated from the leaves and twigs of . Among them, was a biogenetic precursor of 1,8,9-phragmalin limonoid, and represent the first example of degraded A-ring limonoid. The structures of them were elucidated on the basis of one- and two-dimensional NMR spectroscopic data (including H, C-NMR, DEPT, H-H COSY, HSQC, HMBC, and NOESY) and confirmed by high-resolution mass spectrometry.

Directed and Metalation of Naphthalene 1,8-Diamide: Complementing SAr Reactivity for the Synthesis of Substituted Naphthalenes.

Mono- and dianion species of 1,8-naphthalene diamide were generated under -BuLi/TMEDA conditions and trapped with a variety of electrophiles to give 2- and 2,7- substituted products and . Using Suzuki-Miyaura cross-coupling, mono- and di-iodinated products were converted into the corresponding 2-aryl () and 2,7-diaryl () products, respectively. The amide-amide rotation barrier of was established by VT NMR, and the structure of fluorenone structure , obtained by metalation, was secured.

Multistep Photoisomerization of Dimesitylboron-Functionalized Stilbene Analogues.

Dimesitylboron-functionalized stilbene derivatives have been found to undergo an unusual regioselective photoisomerization upon irradiation at 365 nm. Using NMR to follow the photoreaction, the structures of key reaction intermediates and the final products were established. This photoisomerization occurs in four steps: isomerization, Diels-Alder reaction, di-π-methane rearrangement, and ring opening with [1,3]-H migration.