Reactions of Podophyllotoxin with DDQ

Introduction 2, 3-Dichloro-5, 6-dicyanobenzoquinone (DDQ) can react with lignans of the mono- arylidene-butyrolactone1, aryltetralin2, dibenzylbutane3 and aryltetralin-butyrolactone4,5 series. We have studied the reactions of this reagent with podophyllotoxin 1, which is a well-known natural product on account of its long history of use in folk medicine and the biological activity of its many derivatives6. In particular, derivatives of 4-demethyl epipodophyllotoxin are used in cancer chemo…     

Supramolecular [6]chochin and "Big Mac" made from chiral Piedfort assemblies

Facile chemical synthesis of the natural chiral-pool-derived host 1 and its subsequent crystallization ("supramolecular synthesis") from different solvents yielded crystalline assemblies. Crystal structure determinations of five of the so formed solvent-inclusion compounds (1 a-1 e) reveal hexagonal symmetries in four cases. The structural characteristics of these chiral host-guest ensembles with varying stoichiometries can be best described as assemblies formed through intra-pair hydrogen bridges of host molecules into Piedfort pairs of differing complexity. Hitherto undescribed, these Piedfort pairs also form even larger regular assemblies that we designate "Big Mac"-like shapes. In the only nonhexagonal case, six independent host molecules form a huge supramolecular analogue of [6]benzocyclophane, also known as [6]chochin, extending this giant supermolecule through intermolecular hydrogen bonds into macroscopic (mm-size) dimensions. As all these crystals are inherently chiral, and new model systems for solid-state applications can be envisaged.