Indole derivatives for the treatment of osteoporosis

A compound of formula (I):

• 99
• or a salt thereof, or a solvate thereof, wherein:
• Ra represents a group R5 which is hydrogen, alkyl or optionally substituted aryl and Rb represents a moiety of formula (a):
• 100
• wherein X represents a hydroxy or an alkoxy group wherein the alkyl group may be substituted or unsubstituted or X represents a group NRsRt wherein Rs each independently represent hydrogen, alkyl, substituted alkyl, optionally substituted alkenyl, optionally substituted aryl, optionally substituted arylalkyl, an optionally substituted heterocyclic group or an optionally substituted heterocyclylalkyl group, or Rs and Rttogether with the nitrogen to which they are attached form a heterocyclic group;
• R1 represents an alkyl or a substituted or unsubstituted aryl group;
• and R2, R3 and R4 each independently represent hydrogen, alkyl, aryl or substituted aryl
• R6 and R7 each independently represents hydrogen, hydroxy, amino, alkoxy, optionally substituted aryloxy, optionally substituted benzyloxy, alkylamino, dialkylamino, halo, trifluoromethyl, trifloromethoxy, nitro, alkyl, carboxy, carbalkoxy, carbamoyl alkylcarbamoyl, or R6 and R7 together represent methylenedioxy, carbonyldioxy or carbonyldiamino;
• and
• R8 represents hydrogen, hydroxy, alkanoyl, alkyl, aminoalkyl, hydroxyalkyl, carboxyalkyl, carbalkoxyalkyl, carbamoyl or aminosulphonyl;
• providing that such an inhibitor does not include any specific Example disclosed in WO 96/21644.

A process for the preparation of a compound of formula (I) or a salt thereof or a solvate thereof, which process comprises reacting a compound of formula (II):

• 103
• wherein R2, R3, R4, R6, R7 and R8 are as defined in relation to formula (I), with a reagent capable of converting a moiety of formula
• 104
• into a moiety of the above defined formula (a);
• and thereafter, as necessary, carrying out one or more of the following reactions:
• (i) converting one compound of formula (I) into another compound of formula (I);
• (ii) removing any protecting group;
• (iii) preparing a salt or a solvate of the compound so formed.