| abstract |
A compound of formula (I) or (II) is disclosed, whereby, in formulas (I) and (II), R<1> = an optionally-substituted (a) branched or unbranched C1 to C5 alkyl, or (b) branched or unbranched C2 to C5 alkylene, or (c) C3 to C5 cycloalkyl and in formula (II) the bond represented by a dotted line may be either a single- or a double-bond. |