Fig. 1

Core structure of hopanes composed of C-C bonds (lines) and saturated with hydrogen atoms (not shown). The key stereochemical variants occur at C-17, C-21, and C-22 positions. Additional methylation is common at C-2 and C-3. Other structural variants are missing methyl groups. R = H, methyl, ethyl, n-propyl, n-butyl, or n-pentyl group