Chrysomycins, Anti-Tuberculosis C-Glycoside Polyketides from <i>Streptomyces</i> sp. MS751

A new dimeric C-glycoside polyketide chrysomycin F ( 1 ), along with four new monomeric compounds, chrysomycins G ( 2 ), H ( 3 ), I ( 4 ), J ( 5 ), as well as three known analogues, chrysomycins A ( 6 ), B ( 7 ), and C ( 8 ), were isolated and characterised from a strain of Streptomyces sp. obtained from a sediment sample collected from the South China Sea. Their structures were determined by detailed spectroscopic analysis. Chrysomycin F contains two diastereomers, whose structures were further elucidated by a biomimetic [2 + 2] photodimerisation of chrysomycin A. Chrysomycins B and C showed potent anti-tuberculosis activity against both wild-type Mycobacterium tuberculosis and a number of clinically isolated MDR M. tuberculosis strains.