| abstract |
A compound having the structure of formula II: ** Formula ** in which W, A 1, A 2, A 3 and T are defined as follows with the NH of A 1 attached to T, the C = O of A 1 attached to the NH of A 2, the C = O of A 2 attached to the NH of A 3, the C = O of A 3 attached to W, and (W) and (A 1) indicate the site of the union of T to W and A 1 respectively: ** Formula ** |