Design and synthesis of chiral ligands for the stereoselective synthesis of atropisomeric natural products

An investigation into the design and synthesis of chiral helical ligands for application in stereoselective synthesis of atropisomeric natural products by Suzuki coupling reaction has been undertaken. The primary investigation of this thesis was the stereoselective synthesis of chiral vicinal diamine ligands; 2,2'-bipyrrolidine and 2,2'-biindoline scaffolds. The target ligands could be screened inasymmetric Suzuki coupling reaction for synthesis of sterically hindered biaryl natural products. A convenient procedure to synthesise both enantiomers of 2,2'-bipyrrolidine ligands in an enantiomerically well-defined method has been developed taking advantage of the vicinal diol system of commercially available tartaric acid. The required stereochemistry was achieved through stereospecific construction of the 2,2'-bioxirane functionality. The synthesis of both the Boc protected (R,R)- and (S,S)-bipyrrolidine ligands was achieved in four steps with the key step being ring opening of the chiral bioxirane with lithiated acetonitrile as the carbon nucleophile. The (R,R)-2,2'- bipyrrolidine and (S,S)-2,2'-bipyrrolidine scaffolds were synthesised in an overall yield of 14% and 15% from (S,S)-and (R,R)- 2,2'-bioxirane, respectively...