A second carbonyl group at dC 174.0 (C-60 ) was assigned to a carboxylic acid at C-60 due to the key H-50 /C-60 HMBC correlation and then the first sugar derivative was identified as a b-glucuronic acid
A secondcarbonyl group at dC 174.0 (C-60) was assigned to a carboxylic acidat C-60 due to the key H-50/C-60 HMBC correlation and then the firstsugar derivative was identified as a b-glucuronic acid