furan pyrrole thiophene 1 dazole oxazole 呋喃 吡咯 噻吩 咪唑 thiazole pyran pyridine pyrimidine pyrazine 噻唑 吡喃 吡啶 嘧啶 吡嗪 2021/1292021/1/29 furan pyrrole thiophene imidazole oxazole 呋喃 吡咯 噻吩 咪唑 噁唑 thiazole pyran pyridine pyrimidine pyrazine 噻唑 吡喃 吡啶 嘧啶 吡嗪