Identification of unusual 17β(H)-moret-22(29)-ene in lake sediments

An unusual 17β(H)-moret-22(29)-ene in lake sediments was identified for the first time based on the coincidence of its hydrogenation product with 17β(H),21α(H)-moretane in terms of mass spectrum and gas chromatographic retention time. Our survey revealed that 17β(H)-moret-22(29)-ene is present in sediments of 4 acid lakes, 2 brackish lakes and 4 fresh lakes. The abundance of 17β(H)-moret-22(29)-ene relative to diploptene is high in acid lakes, whereas it is very low or almost absent in the latter two types of lakes. This suggests that the formation of 17β(H)-moret-22(29)-ene is closely associated with the acidic conditions of these lake environments. The dehydration of 17β(H),21α(H)-moretan-29-ol is proposed as a possible pathway of formation of 17β(H)-moret-22(29)-ene in lake sediments, although the proposed precursor has yet to be identified.