The enantiomerically pure chlorins 19 and 21 were synthesised from tripyrrolic nickel complex rac-17 and pyrrole building blocks 12 and 16. The pyrroles are annelated with norbornane moieties which contain the chiral information as well as two different functionalities. The functional groups, namely a carboxylic acid ester and a carbonitrile group, of chlorin 21 finally allowed the formation of an
The addition of alkyl isocyanoacetates and isocyanoacetonitrile to alpha,beta-unsaturated sulfones affords a convenient and broad access to pyrroles with unusual substitution patterns (see Scheme 2). The alpha,beta-unsaturated sulfones required as starting materials are easily obtained from different olefines.