Asymmetric Synthesis of β-Hydroxy-α-amino Phosphonic Acid Derivatives via Organocatalytic Direct Aldol Reaction of α-Isothiocyanato Phosphonates with Aldehydes
α-Isothiocyanato phosphonates are first used as nucleophiles to react with aldehydes for the asymmetricsynthesis of β-hydroxy-α-amino phosphonicacid derivatives. The process is catalyzed by a quinine-derived thiourea via cascade aldol/cyclization reaction, affording a wide range of protected β-hydroxy-α-amino phosphonates containing adjacent quaternary-tertiary stereocenters in up to 93% yield, up