Ferruginene C (3) was isolated as a brownish gum and proved to
be a mixture of C-50(R) andC-50 (S) diastereomers. It was assigned
the molecular formula C22H30O3, from theHRESIMS [M H]
peak at m/z 341.2134 (calcd for C22H29O3 341.2122). The 13C and
1H NMR spectroscopic data of 3 were found to be similar to those
reported for 1 (see Tables 1 and 2), but the constitution of the
cyclohexane ringmoiety was different. The 13CNMRspectrumof 3
showed signals of an olefinic methine (C-8) and an olefinic
quaternary carbon (C-9), while in the 1H NMR spectrum, a signal
was revealed for an olefinic methine proton (H-8) instead of the
oxymethine proton present in 1. These observations suggested that
compound 3 has no ether bridge between C-4a and C-5a and no
hydroxy group at C-6 as in ferruginenes A (1) andB(2).The carbon
backbone of 3 was confirmed using COSY, HSQC, and HMBC
spectroscopy (Table 2).