ASYMMETRIC SYNTHESIS AND RETRORACEMISATION OF AMINO ACIDS VIA COPPER(II) COMPLEXES WITH SCHIFF BASES BETWEEN CHIRAL 1-(N,N-DIMETHYLAMINOMETHYL)-2-FORMYLCYMANTRENE AND DIPEPTIDES

Article abstract of DOI:10.1016/0040-4020(80)80064-0

1-(N,N-Dimethylaminomethyl)-2-formylcymantrene (AFCMT) has been resolved into enantiomers through an intermediate formation of diastereomeric complexes with (S)-Ala-(S)-Ala, (S)-Ala-Gly and Gly-(S)-Ala.By the X-ray anomalous dispersion method the absolute configuration of its enantiomers has been determined: (-)₄₃₆ AFCMT-(S), (+)₄₃₆ AFCMT-(R).Alkylation of enantiomeric complexes (R) and (S)-AFCMT-(GlyGly) Cu(II) with acetaldehyde gives, respectively, (R)- and (S)-Thr with an asymmetric yield of 92-98percent and (R)- and (S)-allo-Thr with an asymmetric yield of 95-100percent, only the N-terminal glycine being alkylated.The AFCMT enantiomers were also employed for retroracemisation of (R,S)-Ala-(R,S)-Nva; in this case an excess of (S)-Ala and (R)-Nva is obtained for (S)-AFCMT. (R)- and (S)-AFCMT are not liable to racemisation in the course of the threonine synthesis and retroracemisation of dipeptides and can be repeatedly employed for these transformations.