| 摘要 |
<p>A compound of formula (I) wherein R1 represents O, S or NH; R2 represents a 4-7 membered non-aromatic ring containing 1-3 heteroatoms selected from O, N and S optionally substituted with one or more methyl groups and/or halogen atoms; R3 represents hydrogen, methyl (which may be in either the α or β configuration) or methylene; R4 and R5 are the same or different and each represents hydrogen or halogen; and formula (II) represents a single or a double bond; and salts and solvates thereof.</p> |
