Pleuromutilin derivatives as antimicrobials

A compound of general formula (IA) or (IB):

• in which:
• each of n and m is independently 0, 1 or 2;
• and
• X is selected from —O—, —S(O)—, —SO2—, —CO.O—, —NH—, —CONH—, —NHCONH— and a bond;
• or
• n is 1 or 2 and m is 2 and X is —S—;
• and
• R1 is vinyl or ethyl;
• R2 is optionally substituted quinuclidinyl, azabicyclo[2.2.1]heptyl, azabicyclo[4,3,0]nonyl, azabicyclo[3.2.1]octyl, azabicyclo[3,3,0]octyl, azabicyclo[2.2.2]octyl, azabicyclo[3.2.1]octenyl, azabicyclo[3.3.1]nonyl or azabicyclo[4.4.0]decyl;
• R3 is H or OH;
• or
• the moiety R2(CH2)mX(CH2)nCH2COO at position 14 of (IA) or (IB) is replaced by RaRbC=CHCOO in which one of Ra and Rb is hydrogen and the other is R2 or Ra and Rb together form R2;
• or
• a pharmaceutically acceptable salt thereof.