Nmr spectra of synthetic structures corresponding to those initially r
eported for natural compounds calanolide C[1] and calanolide D[2] show
ed some subtle differences from those of the natural products. Further
analysis has resulted in revision of the structures of the natural co
mpounds, now renamed pseudocalanolides C[3] and D[4]. The absolute ste
reochemistry of pseudocalanolide C was established as [6S,7S,8R] using
the modified Mosher's method.