The 1
H and 13C NMR spectral
data of 2 (Tables 1, 2) were similar to those of alschomine [24], except for
the absence of a methoxy group in 2. Detailed analysis of 1D and 2D NMR
data of 2 suggested a hemiacetal carbon for C-5 in compound 2 instead of
hemiketal in alschomine