abstract |
A compound of formula (Xllla): wherein: L<sup>2</sup> is hydrogen, tert-butoxycarbonyl or benzyl; t is 0 or 1; m and p are, independently, 0, 1 or 2; X is CH<sub>2</sub>, C(O), O, S, S(O), S(O)<sub>2</sub> or NR<sup>37</sup>; provided that when m and p are both 1 then X is not CH<sub>2</sub>; and R<sup>1</sup> has specified values. |