Chiral beta-hydroxyethylamines and their use in the treatment of hyperglycemia

A compound of formula I

• or a pharmaceutically acceptable salt thereof, wherein:
• R1 represents C3-11 alkyl, C3-11 alkenyl, or C3-11 alkynyl each optionally substituted by one or more halo;
• R2 represents C1-2 alkyl, C2 alkenyl, or C2 alkynyl each optionally substituted by one or more halo;
• R3 and R4 each independently represent H or C1-3 alkyl, C2-3 alkenyl, or C2-3 alkynyl each optionally substituted by one or more halo;
• or R3 and R4 may be linked together to form, together with the carbon atom to which they are attached, a 3- to 6-membered ring, which ring optionally is substituted by one or more groups independently selected from halo and C1 alkyl optionally substituted by one or more halo;
• each X independently represents halo, Ra, —CN, —N3, —N(Rb)Rc, —NO2, —ONO2, —ORd, —S(O)pRe or —S(O)qN(Rf)Rg;
• Ra represents C1-6 alkyl, C2-6 alkenyl, or C2-6 alkynyl each optionally substituted by one or more groups independently selected from G;
• each Rb, Rc, Rd, Re, Rf and Rg independently represents H or C1-6 alkyl, C2-6 alkenyl, or C2-6 alkynyl each optionally substituted by one or more groups independently selected from G;
• or alternatively any of Rb and Rc and/or Rf and Rg may be linked together to form, together with the nitrogen atom to which they are attached, a 4- to 6-membered ring, which ring optionally contains one further heteroatom and which ring optionally is substituted by one or more groups independently selected from halo, C1-3 alkyl, C2-3 alkenyl, and C2-3 alkynyl each optionally substituted by one or more halo, and ═O;
• G represents halo, —CN, —N(Ra1)Rb1, ORc1, —S(O)pRd1, —S(O)qN(Re1)Rf1 or ═O;
• each Ra1, Rb1, Rc1, Rd1, Re1 and Rf1 independently represents H or C1-6 alkyl, C2-6 alkenyl, or C2-6 alkynyl each optionally substituted by one or more halo;
• or alternatively any of Ra1 and Rb1 and/or Re1 and Rf1 may be linked together to form, together with the nitrogen atom to which they are attached, a 4- to 6-membered ring, which ring optionally contains one further heteroatom and which ring optionally is substituted by one or more groups independently selected from halo, C1-3 alkyl, C2-3 alkenyl, and C2-3 alkynyl each optionally substituted by one or more halo, and ═O;
• n represents 0 to 5;
• each p independently represents 0, 1 or 2;
• and
• each q independently represents 1 or 2;
• wherein the compound of formula I is present in a diastereomeric excess of at least 90%.