Syntheses of Pterocarpans, II. Synthesis of Both the Enantiomers of Pisatin

Abstract

The first synthesis of (+)‐pisatin [(+)‐11] was achieved by resolving (±)‐6, which in turn was prepared from the isoflavone derivative 1. The unnatural (‐)‐pisatin [(‐)‐11] was also synthesized.

Synthesis of Pterocarpans

“…Removal of the chiral auxiliary followed by acid-catalyzed cyclization, yields natural (-)-pterocarpin and its non-natural enantiomer (scheme 13) [58]. The same procedure has been adapted to the synthesis of pisatin enantiomers [59]. Antus et al [60] tuned up a method for separation of racemic pterocarpans by HPLC on (+)-poly(triphenylmethyl methacrylate)-coated silica gel.…”

Synthesis of Phytohormones, Phytoalexins and Other Biofunctional Molecules of Plant Origin

“…90 Then, in 1989, the enantiomers of pisatin (42) were synthesized, as shown in Figure 2.28. 91 The known isoflavone B 92 was synthesized from sesamol (A) as depicted. The carbonyl group of B was reduced to give a mixture of (±)-C and (±)-D, whose dehydration afforded alkene E. This was oxidized with osmium tetroxide to give (±)-F. Optical resolution of (±)-F could be achieved by HPLC separation of the diastereomers G and H prepared by acylation of (±)-F with (+)-camphor-10-sulfonyl chloride.…”

10-Camphorsulfonyl Chloride

“…Diastereomeric mixtures derived from secondary alcohols have also been analyzed by HPLC. 8 The resolution of a secondary alcohol (4) could be achieved by a selective crystallization of one of the two diastereomeric camphorsulfonate esters. 3…”

“…A general protocol for the HPLC separation of diastereomeric camphorsulfonamides 12 derived from racemic α-amino acids has been developed (eq 1). 13 More complex amino acids, such as (8), were successfully analyzed by this procedure. Synthesis of Chiral Auxiliaries.…”