EP2 receptor agonists

A compound of formula (I):

• or a salt thereof, wherein:
• R5 is an optionally substituted phenyl group where the substituents are selected from the group consisting of:
• unsubstituted C1-4 alkyl, C1-4 alkoxy, —CF3, halo, acyl, amino, and alkoxylene;
• where Q is CH;
• R3 is selected from the group consisting of H, F, Cl, optionally substituted C1-4 alkyl, C1-4 alkoxy, C5-7 aryl and C5-7 aryl-C1-4 alkyl groups;
• R4 is selected from the group consisting of H, F, Cl, optionally substituted C1-4 alkyl, C1-4 alkoxy, C5-7 aryl, and C5-7 aryl-C1-4 alkyl groups;
• R6 is selected from the group consisting of H, F, Cl, optionally substituted C1-4 alkyl, C1-4 alkoxy, C5-7 aryl, and C5-7 aryl-C1-4 alkyl groups;
• D is selected from the group consisting of
• B is selected from the group consisting of
• where one of RP3 and RP4 is —Cm alkylene-R2 and the other of RP3 and RP4 is H, m and n are independently 0 or 1, and m+n=1 or 2;
• and additionally when RP3 is —Cm alkylene-R2, m is 2 or 3, and m+n=2, 3 or 4, and when R2 is tetrazol-5-yl, m+n is 0;
• or
• where one of RP3 and RP4 is —O—CH2—R2, and the other of RP3 and RP4 is H, n is 0;
• RN is H or optionally substituted C1-4 alkyl;
• R2 is either:
• (i) —CO2H (carboxy);
• (ii) —CONH2;
• (iii) —CH2—OH (methoxy);
• or
• (iv) tetrazol-5-yl.