Reduce to the Maximum : Truncated Natural Products as Powerful Modulators of Biological Processes

This account describes several examples from the literature, as well as from our own work, of efforts to reduce the structural complexity of natural products through truncation by organic synthesis. This process, sometimes called diverted total synthesis or function oriented synthesis, also aims to deliver improved compounds for clinical evaluation. The discussed examples from the literature of this type of chemical editing are the truncation of halichondrin B to E7389/eribulin, bryostatin 1 to the bryologs, migrastatin to the migrastatin core, macfarlandin E, and somatostatin (SRIF14) to L-363,301 and octreotide. From our work, efforts on the truncation of anguinomycin/leptomycin, farinosone C to tyrosinol propionamide, and anachelin to the anachelin chromophore are discussed. A hypothesis as to why nature retains apparently nonfunctional appendages on biologically active core structures (related to the pharmacophore) in such ‘less than perfect' natural products is presented. It is proposed that such appendages are generated to increase chemotype plasticity, and that such plasticity might eventually lead to secondary benefits, such as improved physicochemical properties or additional bioactivity.