| A tandem oxidative decarboxylation-elimination protocol has been developed to synthesize peptide enamides from readily available C-terminal peptides. Substrates containing C-terminal tryptophan have been found to form Z-enamides with high selectivity, which has been exploited in expeditious syntheses of the cytotoxic indole-enamide natural products chondriamides A and C.; The first total syntheses of the salicylate enamide natural products oximidines II and III have been achieved by macrocyclic ring-closing metathesis (RCM) and Cu(I)-mediated amidations of vinyl iodides. Effects of the olefin substitution patterns on RCM processes have been studied, which resulted in rational design of acyclic tetraene RCM precursors to construct the 12-membered macrocyclic triene and diene epoxide. Two novel tetrazole sulfone reagents have been developed to convert aldehydes to vinyl iodides under mild conditions.; A novel and convergent strategy has been developed to synthesize the ansamycins, including a one-pot base-mediated silyl-transfer-acylation reaction to facilitate fragment coupling and a tandem nitro-reduction-acyl-transfer process to construct the highly strained bridged bicyclic system. In addition, a biomimetic I(III)-promoted transannular oxidative [4+3] cyclization reaction has been developed to construct the tetracyclic skeleton of the lipoxygenase inhibitor tetrapetalone A and related molecules. |
