Building trans-bicyclo[4.4.0]decanes/decenes in complex multifunctional frameworks: the case for antibiotic development.

Covering: 2000 to 2020. trans-Bicyclo[4.4.0]decane/decene (such as trans-decalin and trans-octalin)-containing natural products display a wide range of structural diversity and frequently exhibit potent and selective antibacterial activities. With one of the major factors in combatting antibiotic resistance being the discovery of novel scaffolds, the efficient construction of these natural products is an attractive pursuit in the development of novel antibiotics. This highlight aims to provide a critical analysis on how the presence of dense architectural and stereochemical complexity necessitated special strategies in the synthetic pursuits of these natural trans-bicyclo[4.4.0]decane/decene antibiotics.

Convenient access to 5-membered cyclic iminium ions: evidence for a stepwise [4 + 2] cycloaddition mechanism.

In situ generation and reaction of novel 5-membered N-tosyl cyclic α,ß-unsaturated iminium ions from readily prepared stable precursors is demonstrated. Formal iminium Diels-Alder cycloaddition proceeded in good yield via a stepwise rather than concerted cycloaddition process, confirmed through the isolation of a Mukaiyama-Michael type intermediate. Relative stereochemistry was determined upon subsequent intramolecular cyclisation under Lewis acid catalysis to afford formal endo 5,6-spirobicyclic adducts, as confirmed by crystallography. Further synthetic elaboration towards complex molecular scaffolds based on the dinoflagellate metabolite portimine, a potent apoptosis inducer, were also developed.

Asymmetric Total Synthesis of the Naturally Occurring Antibiotic Anthracimycin.

The first total synthesis of the potent antibiotic anthracimycin was achieved in 20 steps. The synthesis features an intramolecular Diels-Alder reaction to forge the trans-decalin moiety, and an unprecedented aldol reaction using a complex ß-ketoester to provide the tricarbonyl motif. A Stork-Zhao olefination and Grubbs ring closing metathesis delivered the E/Z-diene and forged the macrocycle. The C2 configuration was set with a base-mediated epimerization, providing access to (-)-anthracimycin.