Hopanes and Neohopanes

Stereoisomers of hopane as the parent hydroearbon of about 100 naturally abundant hopane triterpenes are isolated in small amounts from oil slate and petroleum of various provenanee. Hydroxylated hopanes sueh as (-l-)-6a,22-hopanediol are found to oeeur in some liehens and, assoeiated with (-l-)-22(29)-hopen-6a,2ip-diol, in the roots of Iris missouriensis (Liliaeeae). Neohopanes exemplified by (-l-)-12-neo-hopen-3p-ol from Rhododendron linearifolium (Erieaeeae) rarely oeeur as natural produets. 

Baeteriohopane-32,33,34,35-tetrol and other bio-hopanes partially substituting eho-lesterol in the eell walls of baeteria isolated from eulture eontain an unbranehed polyhydroxylated Cs-Ce aUcyl ehain attaehed to C-30 of the hopane skeleton. Following the death of the baeteria, the hydroxy funetions of bio-hopanes are redueed geo-hopanes whieh are isolated in large amounts from oil slate and other sediments were probably ereated via this pathway some 500 million years ago. 

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