Despite the large number of clerodanes isolated as natural products in the last decade, the correct C-13 NMR chemical shift assignments of some carbons are still in doubt. In order to provide unambiguous assignments of the chemical shifts of clerodane diterpenes, a complete C-13 NMR spectral analysis of methyl (+)-hard-wickiate and 14 hemisynthetic derivatives is reported. (C) 1998 John Wiley & Sons, Ltd.367542544