Patent ID: 6897337

Claim:
A compound of formula I or a salt thereof, wherein R 1 is oxygen or NH 2 ; R 2 is selected from the group consisting of wherein R 3 is hydrogen or n CH 3 ; the dotted line bond represents a second valence bond; m is zero or one; and n, at each occurrence, is 13 or 14; with the provisos that i) when R 1 is NH 2 , the second valence bond represented by the dotted line bond to R 1 is absent and the hydrogen attached to the dotted line bond is present; ii) when R 1 is oxygen, the second valence bond represented by the dotted line bond to R 1 is present and the hydrogen atom attached to the dotted line bond is absent; iii) when R 1 is oxygen, R 2 is B and m is zero; and iv) when R 1 is NH 2 , R 3 is hydrogen or n CH 3 .