Fig. 4: Fatty acid-bartoloside esters are natural products.
From: BrtB is an O-alkylating enzyme that generates fatty acid-bartoloside esters
a LC-HRESIMS analysis of an organic extract of S. salina LEGE 06099 suggests the presence of bartoloside A (1)-palmitic acid esters. b Key HMBC and COSY correlations obtained from 1D and 2D NMR analysis of bartoloside A palmitate 7a purified from S. salina LEGE 06099 cells. c Bartoloside esters found in cells from a 30-day old culture of S. salina LEGE 06099 (as confirmed by HRESIMS/MS analysis) and their relative abundance, determined by LC-HRESIMS (n = 1). d, e Selectivity of the BrtB-catalyzed esterifications leading to bartoloside A palmitates. Shown are LC-HRESIMS analysis-derived conversions (from EIC peak areas and assuming similar ionization behavior) in assays quenched at different time points for the first esterification (d n = 2 independent assays) showing that 7a is the preferred product and for the second esterification (e n = 2 independent assays) indicating that both 7a and 7b are converted into 8 at comparable rates.
