Development of Highly Stereoselective Asymmetric 6π-Azaelectrocyclization of Conformationally Flexible Linear 1-Azatrienes. From Determination of Multifunctional Chiral Amines, 7-Alkyl cis-1-Amino-2-indanols, to Application as a New Synthetic Strategy: Formal Synthesis of 20-Epiuleine

Library-directed solution- and solid-phase synthesis of 2,4-disubstituted pyridines: one-pot approach through 6pi-azaelectrocyclization

An efficient one-pot synthetic procedure for the synthesis of 2,4-disubstituted pyridines has been successfully established. The method proceeds through a 6pi-azaelectrocyclization-aromatization sequence. Using this method, a wide variety of pyridine structures substituted at the 2-position have been rapidly constructed from vinyl stannanes, vinyl iodide, sulfonamide, and a palladium catalyst. The method was further applied to the solid-phase synthesis wherein the use of a "traceless" sulfonamide linker enabled the rapid preparation of a small library of pyridines with high purity, without any chromatographic separation.

PET (positron emission tomography) imaging of biomolecules using metal-DOTA complexes: a new collaborative challenge by chemists, biologists, and physicians for future diagnostics and exploration of in vivo dynamics

Recently, PET has been paid a great deal of attention as a non-invasive imaging method. In this review, the recent advances of PET using biomolecules, such as peptides, monoclonal antibodies, proteins, oligonucleotides, and glycoproteins will be described. So far, PET of biomolecules has been mainly used for diagnosis of cancers. The biomolecules have been conjugated with the DOTA ligand, labeled with radiometals as the beta+ emitter, and targeted to specific tumors, where they have enabled visualization of even small metastatic lesions, due to the high sensitivity of the PET scanners. Some of the biomolecules have been used not only for PET diagnosis, but also for radiotherapeutic treatments by simply changing the radiometals to beta(-) emitters. Collaborative work between chemists, biologists, and physicians will be important for the future of biomolecule-based targeting and diagnosis.

Aza- and Carbo-[3 + 3] Annulations of Exo-Cyclic Vinylogous Amides and Urethanes. Synthesis of Tetrahydroindolizidines and An Unexpected Formation of Hexahydroquinolines

[3 + 3] Annulations of exo-cyclic vinylogous amides and urethanes with vinyl iminium salts are described here. We observed an intriguing dichotomy in their reaction pathways. For pyrrolidine- and azepane-based vinylogous amides or urethanes, aza-[3 + 3] annulation would dominate to give tetrahydroindolizidines, whereas, unexpectedly, for piperidine-based vinylogous amides or urethanes, carbo-[3 + 3] annulation was the pathway, leading to hexahydroquinolines. The origin for such a contrast is likely associated with a switch in the initial reaction pathway between C-1,2-addition and C-1,4-addition.

Application of a 6pi-1-azatriene electrocyclization strategy to the total synthesis of the marine sponge metabolite ageladine A and biological evaluation of synthetic analogues

A 12-step synthesis of the angiogenesis inhibitory marine metabolite ageladine A is reported. The key steps include a 6pi-1-azatriene electrocyclization for formation of the pyridine ring and a Suzuki-Miyaura coupling of N-Boc-pyrrole-2-boronic acid with a chloroimidazopyridine. In addition, an assessment of the biological activity of a variety of synthetic analogues of ageladine A prepared during this synthesis is described.

Total synthesis of ageladine A, an angiogenesis inhibitor from the marine sponge Agelas nakamurai

[reaction: see text] A 12-step total synthesis of the tricyclic heteroaromatic marine metabolite ageladine A has been achieved using a 6pi-azaelectrocyclization and a Suzuki-Miyaura coupling of N-Boc-pyrrole-2-boronic acid with a chloropyridine as key steps.

Synthesis of 2,4,6-Trisubstituted Chiral Piperidines and (−)-Dendroprimine by One-Pot Asymmetric Azaelectrocyclization Protocol

[reaction: see text] Stereocontrolled synthesis of 2,4,6-trisubstituted piperidine diastereomers has been realized from common intermediates, obtained by a one-pot azaelectrocyclization protocol. Based on the method, the asymmetric synthesis of an indolizidine alkaloid, (-)-dendroprimine, was achieved.

Development of a One-Pot Asymmetric Azaelectrocyclization Protocol: Synthesis of Chiral 2,4-Disubstituted 1,2,5,6-Tetrahydropyridines

[reaction: see text] A one-pot procedure for tetracyclic chiral aminoacetals, the useful precursors for substituted piperidine synthesis, has been established via Stille-Migita coupling, 6pi-azaelectrocyclization, and aminoacetal formation from readily prepared vinylstannanes, vinyliodides, and cis-aminoindanol derivatives. Based on the method, chiral 2,4-disubstituted 1,2,5,6-tetrahydropyridines, bearing a variety of aromatic substituents at the C-2 position, have been prepared.