Asymmetric Synthesis of C-Aliphatic Homoallylic Amines and Biologically Important Cyclohexenylamine Analogues

Asymmetric cinnamylation of N-tert-butanesulfinyl imines with cinnamyl acetates: total syntheses of (+)-lycoricidine and (+)-7-deoxypancratistatin

Highly diastereoselective palladium catalyzed cinnamylation of N-tert-butanesulfinyl imines with cinnamyl acetates has been established to provide enantioenriched β-aryl homoallylic amines. The synthetic application of this stragety has been successfully demonstrated in the concise total syntheses of antitumor natural products (+)-lycoricidine and (+)-7-deoxypancratistatin.

Single or Synergistic Kinetic Resolutions of Chiral Allylalanes: Two Complementary Routes for the Asymmetric Synthesis of Syn Homoallylamines

Two strategies based on kinetic resolution(s) of chiral alanes and providing enantioenriched syn homoallylamines are reported. The first implies a single kinetic resolution of the alane using camphor; the second requires two sequential kinetic resolutions using the synergistic combination of (-)-camphor/(R)-tert-butylsulfinamide-derived imines. This syn selectivity, specific to the use of allyaluminum, opens the way to the preparation of valuable building blocks as illustrated by the synthesis of (+)-epilupinamine.

Design, synthesis, and applications of chiral N-2-phenyl-2-propyl sulfinyl imines for group-assisted purification (GAP) asymmetric synthesis

A new chiral (Rs)-2-phenyl-2-propyl sulfinamide has been designed and synthesized; its derived aldimines and ketimines have been applied for asymmetric addition reaction with allylmagnesium bromide. The reaction was conveniently performed at room temperature to give a series of homoallylic amines in high yields (up to quant) and diastereoselectivity (up to >99% de). The pure products were obtained by relying on group-assisted purification (GAP) chemistry to avoid traditional purification methods of column chromatography or recrystallization. The conversion of disulfide to (R(s))-thiosulfinate which contains a newly generated polar group was also confirmed to be of the GAP chemistry in which washing crude product can generate pure enantiomer. The absolute stereochemistry has been determined by X-ray analysis.

Asymmetric allylboration of acyl imines catalyzed by chiral diols

Chiral BINOL-derived diols catalyze the enantioselective asymmetric allylboration of acyl imines. The reaction requires 15 mol % (S)-3,3'-Ph2-BINOL as the catalyst and allyldiisopropoxyborane as the nucleophile. The reaction products are obtained in good yields (75-94%) and high enantiomeric ratios (95:5-99.5:0.5) for aromatic and aliphatic imines. High diastereoselectivities (diastereomeric ratio > 98:2) and enantioselectivities (enantiomeric ratio > 98:2) are obtained in the reactions of acyl imines with crotyldiisopropoxyboranes. This asymmetric transformation is directly applied to the synthesis of Maraviroc, the selective CCR5 antagonist with potent activity against HIV-1 infection. Mechanistic investigations of the allylboration reaction including IR, NMR, and mass spectrometry studies indicate that acyclic boronates are activated by chiral diols via exchange of one of the boronate alkoxy groups with activation of the acyl imine via hydrogen bonding.