Novel side chain methylated and hexacyclic hopanes: Identification by synthesis, distribution in a worldwide set of coals and crude oils and use as markers for oxic depositional environments

► Novel isohopanes and hexacyclic hopanes have been identified in coal and crude oils. ► Isohopanes are particularly abundant in coal and coal-generated oils. ► Isohopanes have a stereoisomer distribution similar to that of regular geohopanes. ► Isohopanes appear more resistant to biodegradation than regular hopanes. ► 25-Norisohopanes were detected in oils containing regular 25-norhopanes.