Chiral Indolizinium Salts Derived from 2-Pyridinecarbaldehyde-First Diastereoselective Syntheses of (-)-1-epi-lentiginosine.

The first diastereoselective synthesis of (-)-1-epi-lentiginosine from a common chiral trans-epoxyamide derived from 2-pyridincarbaldehyde is reported. This methodology involves a sequential oxirane ring opening and intramolecular 5-exo-tet cyclization of tosylate trans-epoxyalcohol to afford a diastereomeric mixture of indolizinium salts in a one-pot fashion, followed by regio- and diastereospecific pyridinium ring reduction.

Diastereoselective synthesis of new zwitterionic bicyclic lactams, scaffolds for construction of 2-substituted-4-hydroxy piperidine and its pipecolic acid derivatives.

The synthesis of new chiral highly functionalized zwitterionic bicyclic lactams starting from acyclic ß-enaminoesters derived from (R)-(-)-2-phenylglycinol is described. The key step involved an intramolecular non-classical Corey-Chaykovsky ring-closing reaction of the corresponding sulfonium salts derived from ß-enaminoesters. This methodology permits the generation of two or three new stereogenic centers with high diastereoselectivity. The utility of these intermediates was demonstrated by the stereocontrolled total synthesis of cis-4-hydroxy-2-methyl piperidine and its corresponding pipecolic acid derivative.

(R)-3,3-Diethyl-1-(2-hy-droxy-1-phenyl-eth-yl)piperidin-2-one.

In the title compound C(17)H(25)NO(2), the piperidin-2-one ring adopts an envelope conformation with the C atom in the 5-position as the flap. The crystal packing is stabilized by inter-molecular O-H⋯O hydrogen bonds, building a infinite chain along the b-axis direction. C-H⋯π inter-actions further stabilize the crystal packing.

(S)-(-)-2-(1H-Indol-3-yl)-N-(1-phenyl-eth-yl)acetamide.

In the title compound, C(18)H(18)N(2)O, the dihedral angle between the indole system and the phenyl ring is 17.2 (2)°. The crystal packing features two N-H⋯O hydrogen bonds, which link the mol-ecules into layers parallel to (001). The absolute configuration was determined by the synthetic procedure and was set according to the starting material.

(7aS)-(-)-Dimeth-yl(1-oxido-3-oxo-5,6,7,7a-tetra-hydro-3H-pyrrolizin-2-yl)sulfonium.

In the zwitterionic title compound, C(9)H(13)NO(2)S, the pyrrolidine heterocycle adopts an envelope conformation (with the C atom in the 7-position as the flap). The negative charge is delocalized over the two carbonyl groups and the C atom connecting them. The positive charge is located on the S atom. Two inter-molecular C-H⋯O inter-actions are observed. The molecular geometry at the S atom is trigonal pyramidal.

(R)-(+)-Dimeth-yl[4-oxido-2-oxo-1-(1-phenyl-eth-yl)-1,2,5,6-tetra-hydro-pyridin-3-yl]sulfonium.

In the title zwitterionic compound, C(15)H(19)NO(2)S, the six-membered heterocycle adopts a sofa conformation. The negative charge is delocalized along the carbonyl and enolate system on the ring and the positive charge is localized on the S atom. Two inter-molecular C-H⋯O inter-actions help to establish the packing.

(1'S,2R,3R)-(-)-2-Hydr-oxy-3-morpholino-3-phenyl-N-(1'-phenyl-ethyl)propion-amide.

In the title compound, C(21)H(26)N(2)O(3), the morpholine ring has a chair conformation and the dihedral angle between the two phenyl rings is 59.0 (3)°. The crystal packing is stabilized by inter-molecular O-H⋯O hydrogen bonds, generating a ribbon structure along the a axis. An intra-molecular N-H⋯O contact is also present.