Stereocontrolled Synthesis of Substituted Chiral Piperidines via One-Pot Asymmetric 6π-Azaelectrocyclization: Asymmetric Syntheses of (−)-Dendroprimine, (+)-7-Epidendroprimine, (+)-5-Epidendroprimine, and (+)-5,7-Epidendroprimine

The asymmetric one-pot 6π-azaelectrocyclization of alkenyl vinyl stannane, ethyl (<i>Z</i>)-2-iodo-4-oxobutenoate, and (−)-7-isopropyl-<i>cis</i>-aminoindanol in the presence of a Pd(0) catalyst stereoselectively produced the tetracyclic aminoacetal compounds, resulting from the four-bond formation accompanying by controlling the stereochemistry at the two asymmetric centers. The produced cyclic aminoacetals can be regarded as synthetic precursors of substituted chiral piperidines, and the syntheses of 2,4- and 2,4,6-substituted piperidines were realized from the obtained aminoacetals by the stereoselective hydrogenation of the double bond conjugated with the C-4 ester group and alkylation at the aminoacetal moiety. In addition, the stereoselective synthesis of an indolizidine alkaloid, (−)-dendroprimine, and its three stereoisomers, (+)-7-epidendroprimine, (+)-5-epidendroprimine, and (+)-5,7-epidendroprimine, were achieved

Stereocontrolled Synthesis of Substituted Chiral Piperidines via One-Pot Asymmetric 6π-Azaelectrocyclization: Asymmetric Syntheses of (−)-Dendroprimine, (+)-7-Epidendroprimine, (+)-5-Epidendroprimine, and (+)-5,7-Epidendroprimine

The asymmetric one-pot 6π-azaelectrocyclization of alkenyl vinyl stannane, ethyl (<i>Z</i>)-2-iodo-4-oxobutenoate, and (−)-7-isopropyl-<i>cis</i>-aminoindanol in the presence of a Pd(0) catalyst stereoselectively produced the tetracyclic aminoacetal compounds, resulting from the four-bond formation accompanying by controlling the stereochemistry at the two asymmetric centers. The produced cyclic aminoacetals can be regarded as synthetic precursors of substituted chiral piperidines, and the syntheses of 2,4- and 2,4,6-substituted piperidines were realized from the obtained aminoacetals by the stereoselective hydrogenation of the double bond conjugated with the C-4 ester group and alkylation at the aminoacetal moiety. In addition, the stereoselective synthesis of an indolizidine alkaloid, (−)-dendroprimine, and its three stereoisomers, (+)-7-epidendroprimine, (+)-5-epidendroprimine, and (+)-5,7-epidendroprimine, were achieved

Crystal Engineering of Self-Assembled Porous Protein Materials in Living Cells

Crystalline porous materials have been investigated for development of important applications in molecular storage, separations, and catalysis. The potential of protein crystals is increasing as they become better understood. Protein crystals have been regarded as porous materials because they present highly ordered 3D arrangements of protein molecules with high porosity and wide range of pore sizes. However, it remains difficult to functionalize protein crystals in living cells. Here, we report that polyhedra, a natural crystalline protein assembly of polyhedrin monomer (PhM) produced in insect cells infected by cypovirus, can be engineered to extend porous networks by deleting selected amino acid residues located on the intermolecular contact region of PhM. The adsorption rates and quantities of fluorescent dyes stored within the mutant crystals are increased relative to those of the wild-type polyhedra crystal (WTPhC) under both <i>in vitro</i> and <i>in vivo</i> conditions. These results provide a strategy for designing self-assembled protein materials with applications in molecular recognition and storage of exogenous substances in living cell as well as an entry point for development of bioorthogonal chemistry and <i>in vivo</i> crystal structure analysis