Patent ID: 7226918

Claim:
A compound of formula Ia: or an isomer, salt, chemically protected for or prodrug thereof, wherein: R 1 and R 2 are independently hydrogen, an optionally substituted C 1-7 alkyl group, C 3-20 heterocyclyl group, or C 5-20 aryl group, or may together form, along with the nitrogen atom to which they are attached, an optionally substituted heterocyclic ring having from 4 to 8 ring atoms; R 3 and R 4 together are -A-B-, which collectively represent a fused benzene ring, substituted at the 8-position with an optionally substituted tricylic C 3-20 heterocyclic group or at the 6-, 7- or 8-position with a phenyl group substituted by phenyl.