| 摘要 |
<p>A compound of formula (IA) or (IB) in which R1 is an optionally substituted heteroaryl group which comprises a five membered heteroaromatic ring which has at least one nitrogen atom and which is linked via a nitrogen atom; R2 is vinyl or ethyl; R3 is H, OH or F, and R4 is H, or R3 is H and R4.</p> |
