Synthesis of Optically Pure Enantiomers Using Chiral Ureas

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Using Chiral urea derivatives, the following diastereoselective synthesis and a convenient separation of diastereomers by a conventional column chromatography were accomplished.(1) Diastereoselective aldol addition reaction using chiral acylureas; This method was applied to the two step synthesis of (+) Blastmaycinolactol.(2) Chiral carbodiimide as an effective chiral derivatizing agent; N,N'-bis[(s)-l-phenylethyl]- carbodiimide was found to be a very useful chiral derivatizing agent, which made an easy separation of diastereomers of alpha-amino acids and alpha-halo acids by a conventional column chromatography.(3) Highly enantioselective Aldol reaction using imidazolidinone as a new chiral Auxiliary; Aldol addition reaction of almost perfect stereo control (>99% diastereoselectivity) was developed.(4) Chiral hydantoin as a new dienophile for Diels-Alder Reaction; A new synthetic method of chiral exo-methylenehydantoin from chiral carbodiimides and alpha-ketoacids was established and the exo-methylenehydantoin thus obtained was applied for Diels-Alder reaction to prepare chiral bicyclic alpha-amino acid derivatives.(5) Conjugated addition reaction of alkylaluminum compounds to exo-methylenehydantoin; Mono and Double conjugated additions of aluminum reagents to exo-methylenehydantoin were found out and this two modes of addition was effectively controlled.(6) Three component coupling reaction carbodiimide, monomethyl maleate, and alcohol; This coupling afforded N-(aminocarbony)aspartates.(7) Asymmetric type II photocyclization of acrylylureas; It was found that the stereochemistry of the carbon atom where a hydrogen atom to be abstracted in type II photocyclization was retained to give a chiral beta-lactam.