Synthesis and Stereochemical Assignment of Conioidine A: DNA- and HSA-Binding Studies of the Four Diastereomers.

Conioidine A (), isolated in 1993 with unknown relative and absolute configuration, was suggested to be a DNA-binding compound by an indirect technique. Four stereoisomers of conioidine A have been synthesized from d- and l-proline, and the natural product has been identified as possessing (4,6) absolute configuration. Binding of the conioidine diastereomers to calf thymus DNA (CT DNA) and human serum albumin (HSA) has been investigated by fluorescence spectroscopy and isothermal titration calorimetry (ITC).

Ring Expansion, Ring Contraction, and Annulation Reactions of Allylic Phosphonates under Oxidative Cleavage Conditions.

Oxidative cleavage of cycloalkenylalkylphosphonates 1 followed by treatment with base gives rise to homologated cycloalkenones 2 in good to excellent yields. Subjecting cycloalk-2-enylphosphonates 3 to identical conditions provides the one-carbon ring-contracted compounds 4 in excellent yields. Oxidative cleavage of γ,δ-unsaturated ketophosphonates 6 followed by treatment with base affords 2-cyclopenten-1-ones 7 in good overall yields.