Substituted heterocyclic compounds

A compound of Formula I:

• wherein:
• R1, R2, R3, R4, R5, R6, R7, and R8 are hydrogen, lower alkyl, or —C(O)R;
• in which R is —OR9 or —NR12R13, where R12 and R13 are hydrogen or lower alkyl;
• or
• R1 and R2, R3 and R4, R5 and R6, R7 and R8, when taken together with the carbon to which they are attached, represent carbonyl;
• or
• R1 and R5, or R1 and R7, or R3 and R5, or R3 and R7, when taken together form a bridging group —(CR14R15)n—, in which n is 1, 2 or 3, and R14 and R15 are independently hydrogen or lower alkyl;
• with the proviso that
• (i) the maximum number of carbonyl groups is 2;
• and
• (ii) the maximum number of bridging groups is 1;
• R9 and R11 are independently optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted cycloalkyl, optionally substituted aryl, or optionally substituted heteroaryl;
• R10 is hydrogen or lower alkyl;
• T is oxygen, sulfur, or ═NR16, in which R16 is hydrogen, lower alkyl, cyano, lower alkoxy, or C(O)OR17, in which R17 is lower alkyl;
• X is —N< or —NH—CH<;
• Y is optionally substituted alkylene of 1-3 carbon atoms;
• and
• Z is —O—, —S—, —N(R18)— where R18 is hydrogen or lower alkyl, or a covalent bond.