Diphenylmethyl compounds useful as muscarinic receptor antagonists

A compound of formula I:

• wherein:
• each R1 and R2 are independently selected from (1–4C)alkyl, (2–4C)alkenyl, (2–4C)alkynyl, (3–6C)cycloalkyl, cyano, halo, —ORa, —SRa, —NRaRb, —S(O)Rc and —S(O)2Rc;
• where each Ra and Rb independently represents hydrogen, (1–4C)alkyl, (2–4C)alkenyl, (2–4C)alkynyl or (3–6C)cycloalkyl;
• each Rc independently represents (1–4C)alkyl,(2–4C)alkenyl, (2–4C)alkynyl or (3–6C)cycloalkyl;
• or two adjacent R1 groups or two adjacent R2 groups are joined together to form (3–6C)alkylene, (2–4C)alkylene-O— or —O-(2–4C)alkylene-O—;
• a and b each independently are 0 or an integer of from 1 to 5;
• each R3 independently is fluoro or (1–4C)alkyl;
• c is 0 or an integer of from 1 to 3;
• R4a and R4b are independently selected from hydrogen, (1–4C)alkyl, and phenyl-(1–4C)alkyl;
• or R4a and R4b together with the nitrogen atom to which they are attached form a (3–6C)heterocyclic ring optionally containing one additional heteroatom selected from nitrogen, oxygen or sulfur and wherein the heterocyclic ring is unsubstituted or substituted with 1 or 2 substituents selected independently from (1–4C)alkyl and fluoro;
• e is 1 or2;
• m is 4, 5 or 6;
• R5 is selected from hydrogen, (1–4C)alkyl, and (3–4C)cycloalkyl;
• R6 is hydrogen or an unbranched (1–4C)alkyl;
• or R6 and R8 are joined, together with the atoms to which they are attached, to form a pyrrolidin-2-yl group;
• R7 is selected from hydrogen, (1–6C)alkyl, (3–6C)cycloalkyl, —CH2Ar1, —CH2CH2——CH2CH2—O-(1–4C)alkyl;
• wherein Ar1 represents phenyl or (3–5C)heteroaryl, wherein the phenyl or heteroaryl group is unsubstituted or substituted with from 1 to 3 substituents selected independently from halo, (1–4C)alkyl and (1–4C)alkoxy;
• wherein each alkyl and alkoxy is optionally substituted with from 1 to 3 fluoro substituents;
• and
• R8 is hydrogen or (1–6C)alkyl;
• or R7 and R8 together with the nitrogen atom to which they are attached form a pyrrolidin-1-yl, piperidin-1-yl, morpholin-1-yl or thiomorpholin-1-yl group;
• wherein each alkyl group in R1, R2, R3, R4a, R4b, R5, R6, R7, R8 and Ra-c is optionally substituted with from 1 to 5 fluoro substituents;
• or a pharmaceutically acceptable salt or solvate or stereoisomer thereof.