Following up on my post commenting on Prof Bob Pettit’s life and accomplishments, I have scanned a few photos from 1994 that I took in a Cancer Research Institute (CRI) lab.
A few things stand out from the lab: (1) the absolute focus on bioassay-guided isolation and (2) Kupchan-type partitions followed by Sephadex LH-20 chromatography using a variety of solvent systems. For example, see the isolation of cephalostatins 10 and 11 from a 1994 JNP paper: solvent partitioning, followed by Sephadex LH-20 columns eluting with (1) MeOH, (2) CH2Cl2-MeOH [3:2], (3) hexane-toluene-MeOH [3:1:1], (4) hexane-iPrOH-MeOH [8:1:1], and (5) hexane-CH2Cl2-MeOH [5:1:1], with the last step being reversed-phase HPLC.
Having this type of steely focus on bioassay-guided isolation, really helped to lay the groundwork for my subsequent teams and I to be able to successfully biologically purify active compounds that account for the extract’s activity – even if it was not straightforward. I also remember a list of crystallisation solvents that Bob used to carry around with him. One started at the top and worked your way through the list until crystals were obtained that were suitable for structure confirmation using X-ray crystallography.