Synthetic Approach to Chromone and Flavonoid Piperidine Alkaloids.

Despite the enormous importance of chromone and flavonoid piperidine alkaloids, a general method for their synthesis has not been described. Accordingly, from simple tetrahydro-3-pyridinemethanols () and phenol derivatives (), a synthetic approach to chromone and flavonoid piperidine alkaloids is presented. The access to a novel chromone and flavonoid alkaloid precursors 4-(2-hydroxyphenyl)-3-methylenepiperidines () is achieved in only two steps: Mitsunobu reaction followed by an intramolecular C-H phenolization via an aromatic Claisen rearrangement of the respective Mitsunobu adducts ().

Chiron approach toward the synthesis of the fused tricyclic core of epi-parvistemonine A.

A stereoselective synthesis of fused tricyclic framework of epi-parvistemonine A from D-glucono-δ-lactone is described. The synthetic strategic is based on the stereoselective construction of the 7-membered cyclic skeleton via a cross-metathesis reaction followed by a Michael type cyclization promoted by TfO.

Ethyl (3)-3-[(3a,5,6,6a)-6-hy-droxy-2,2-di-methyl-tetra-hydro-furo[4,5-][1,3]dioxol-5-yl]-3-{(3)-3-[(3a,5,6,6a)-6-hy-droxy-2,2-di-methyl-tetra-hydro-furo[4,5-][1,3]dioxol-5-yl]-5-oxoisoxazolidin-2-yl}propano-ate chloro-form monosolvate.

The title compound, CHNO·CHCl, was obtained as a product of a double aza-Michael addition of hydroxyl-amine on a Chiron with a known absolute configuration. The enanti-opure compound crystallized as a chloro-form solvate, in space group 1, and diffraction data were collected at room temperature with Ag α radiation. The Flack parameter refined to = -0.

Deciphering the hydrogen-bonding scheme in the crystal structure of triphenylmethanol: a tribute to George Ferguson and co-workers.

The crystal structure of triphenylmethanol, CHO, has been redetermined using data collected at 295 and 153 K, and is compared to the model published by Ferguson et al. over 25 years ago [Ferguson et al. (1992).

Can an n → π* Interaction Provide Thermodynamic Stability to Naturally Occurring Cephalosporolides?

The stereocontrolled synthesis of naturally occurring products containing a 5,5-spiroketal molecular structure represents a major synthetic problem. Moreover, in a previous work, the stereocontrolled synthesis of cephalosporolide E (ceph E), which presumably was obtained from its epimer congener (ceph F) through an acid-mediated equilibration process, was reported. Consequently, we performed a theoretical investigation to provide relevant information regarding the title question, and it was found that the higher thermodynamic stability of ceph E, relative to ceph F, is caused by an n → π* interaction between a lone electron pair of the oxygen atom of the spiroketal ring (n) and the antibonding orbital of the carbonyl group (π*).

Endo-selective quenching of hexahydropyrrolo[2,3-b]indole-based N-acyliminium ions.

Radical decarboxylation of L-tryptophan-derived (2S,3aR,8aS)-8-arylsulfonyl-1,2-di(methoxycarbonyl)-1,2,3,3a,8,8a-hexahydro-2H-pyrrolo[2,3-b]indoles 8 and 9 in the presence of diphenyl diselenide results in the endo-selective formation of (2R,3aR,8aS)-8-arylsulfonyl-1-methoxycarbonyl-2-phenylselenyl-1,2,3,3a,8,8a-hexahydro-2H-pyrrolo[2,3-b]indoles 10 and 11. These selenides, in conjunction with Lewis acids, serves as precursors to the corresponding N-acyl iminium ions, which undergo selective endo-face quenching by allyltributylstannane, allyltrimethylsilane, propargyltrimethylsilane, and trimethylsilylcyanide. Stereochemical assignments rest on NMR data and crystallographic studies.