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The enantiomerically pure pyrrolidine diester (Ring A) is a useful building block for the synthesis of chiral tolyporphin and other hydroporphyrin compounds. This was synthesized from enantiomerically pure lactam-lactone. Treatment of optically active aromatic amines with bislactone gave pairs of N-alkylated lactam-lactone diastereomers. These diastereomers were separated by MPL chromatography and debenzylated using ceric (IV) ammonium nitrate (CAN) to yield enantiomerically pure lactam-lactone isomers. The ( )-lactam-lactone enantiomer was treated with methanolic cyanide solution which selectively opened lactone ring to form the cyano lactam. This was further transformed into the cis- and trans-thiocyanolactam isomers. The configurations of these isomers were established by NOE experiment which was confirmed by X-ray measurement and theoretical means(ab initio calculations). Coupling of cis-thiocyanolactam with bromomalonic diester according to the sulphide contraction method gave the enantiomerically pure pyrrolidine diester.
About the author
Dr.Genevieve Etornam Adukpo is a lecturer at the University of Cape Coast, Ghana. She had her BSc Chemistry, Dip.Sc.Ed, MPhil Natural Product in Cape Coast, Ghana and PhD (Synthetic Organic Chemistry) in Bremen, Germany. Her research fields of interest are isolation, characterization bioassay studies and synthesis of bioactive compounds.
