Facile and rapid access to linear and truncated microcystin analogues for the implementation of immunoassays

A series of simplified microcystin-LR analogues based on Adda [(2S,3S,8S,9S,4E,6E)-3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldecadienoic acid] or its corresponding aldol precursor linked to a polypeptide moiety have been synthesised and assessed for their binding affinity by the monoclonal antibody mAb MC159, an anti-microcystin-LR mAb recently selected by us for the detection of microcystins through various immunoassay formats. Some modifications have been brought to the enantiospecific synthesis of N-Boc-Adda developed by Pearson et al. (Org. Lett., 2000, 2, 2901) which enabled us to access in an economical and time-saving manner a small library of MC-LR linear analogues. Among which Adda was chosen to synthesise, as an illustrative example, a fluorescent probe derived from this beta-amino acid. This probe was subsequently solid-phase immobilised by means of oxime ligation in order to lead to biochips suitable for microcystin detection through the SPIT-FRI method.