| 主权项 |
1. A compound represented by one of the following formulas: wherein: Y1a represents O, S, NR4a, wherein R4a represents optionally substituted C1-C4 alkyl; or C(R4c)2, wherein each R4c in (R4c)2 represents hydrogen or optionally substituted C1-C4 alkyl; Y1b represents O, S, NR5a, wherein R5a represents optionally substituted C1-C4 alkyl; or C(R5c)2, wherein each R5c in (R5c)2 represents hydrogen or optionally substituted C1-C4 alkyl; each of Y2a, Y2b, Y2c, and Y2d independently represents N, NR6a, or CR6b, wherein each of R6a and R6b is independently absent or independently represents hydrogen or optionally substituted C1-C4 alkyl; and each of Y3a, Y3b, Y3d, Y4b, and Y4d independently represents N, O, S, NR6a, CR6b, wherein each of R6a and R6b is independently absent or independently represents hydrogen or optionally substituted C1-C4 alkyl. |
