| abstract |
1. The compound of formula I: or a pharmaceutically acceptable salt thereof, wherein independently in each case: Y is OH or NH; and X is COJ; where J is H or C-C 1-6 alkyl; R is H, OH, OCH, or two R taken together form -OCHO- or -OCFO-; R is H or up to two C-C 1-6 alkyls ; R represents H or halogen; and R is H or CC alkyl; or Y and X, taken together, form a compound of formula II: or a pharmaceutically acceptable salt thereof, wherein independently in each case: R is H, OH, OCH, or two R, taken together, form -OCHO - or —OCFO—; R represents H or up to two C-C 1-6 alkyls; R represents H or halogen; and R is H or CC alkyl; R is H or C-Calkyl; Y is O or NR; and R 1 is H or C 1-6 alkyl. 2. The compound according to claim 1 of formula I, wherein two R, taken together, form OCFO-, R is H, and R is F.3. A compound according to claim 1 of formula I, wherein two R, taken together, form —OCFO—, R is H, R is F, and R is CH.4. A compound according to claim 1, wherein two R, taken together, form —OCFO—, R is H, R is F, R is CH, and X is COH. 5. A compound according to claim 1, wherein two R are taken together to form —OCFO—, R is H, R is F, R is CH, X is COH, and Y is OH. 6. A compound according to claim 1 of formula II, wherein two R, taken together, form —OCFO—, R is H, and R is F.7. The compound according to claim 1 of formula II, wherein two R, taken together, form —OCFO—, R is H, R is F, and R is CH.8. A compound according to claim 1, having |