1-aryl-1-hydroxy-2,3-diamino-propyl amines, 1-heteroaryl-1-hydroxy-2,3-diamino-propyl amines and related compounds having analgesic and/or immuno stimulant activity

1. A compound of the formula

or a pharmaceutically acceptable salt thereof; where:

R 1 is H or alkyl of 1 to 6 carbons;

R 2 is H, alkyl of 1 to 6 carbons or the R 1 and R 2 groups together with the nitrogen form a saturated or unsaturated 4, 5, 6 or 7 membered ring that optionally includes one or two heteroatoms independently selected from N, O and S, said 4, 5, 6 or 7 membered ring optionally being substituted with a halogen or with an alkyl group having 1 to 6 alkyl groups;

R 3 is independently selected from H, alkyl of 1 to 20 carbons, aryl or heteroaryl, aryl-alkyl or heteroaryl-alkyl where the alkyl moiety has 1 to 4 carbons, cycloalkyl of 3 to 6 carbons, said aryl or heteroaryl groups being optionally substituted with 1 to 3 groups independently selected from the group consisting of halogen, alkyl of 1 to 6 carbons, alkoxy of 1 to 6 carbons and thioxy of 1 to 6 carbons, or R 3 is CO—R 7 or CO—O—R 7 where R 7 is H, alkyl of 1 to 20 carbons, benzyl, alkyl of 1 to 20 carbons substituted with and NH 2 group, with a NHCOOalkyl or with an NH-COalkyl group where the alkyl group has 1 to 6 carbons, or R 7 is aryl, heteroaryl, aryl-alkyl or heteroaryl-alkyl where the alkyl moiety is branched or unbranched and has 1 to 4 carbons, said aryl or heteroaryl groups being optionally substituted with 1 to 3 groups independently selected from the group consisting of halogen, alkyl of 1 to 6 carbons, alkoxy of 1 to 6 carbons and thioxy of 1 to 6 carbons;

R 4 is H, alkyl of 1 to 6 carbons or CO—R 8 where R 8 is alkyl of 1 to 6 carbons;

the wavy lines represent bonds connected to carbons having R or S configuration, and

R 10 is

where the * indicates the carbon atom to which the remaining moiety of the molecule is attached;

R 5 and R 6 independently are H, alkyl of 1 to 6 carbons, halogen, alkoxy of 1 to 6 carbons or the R 5 and R 6 groups together with the atoms to which they are attached jointly form a heterocyclic ring, the heterocyclic ring having 5 or 6 atoms in the ring and 1 to 3 heteroatoms independently selected from N, O and S, and said carbocyclic or heterocyclic ring jointly formed by R 5 and R 6 being optionally substituted with 1 to 6 R 9 groups where R 9 is independently selected from halogen, alkyl of 1 to 6 carbons, alkoxy of 1 to 6 carbons.

2. A method of treating pain in a mammal, the method comprising the step of administering to said mammal in need of such treatment a compound in accordance with claim 1 or a pharmaceutically acceptable salt thereof.

3. A pharmaceutical composition comprising a compound in accordance with claim 1 or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable excipient.

4. The method of claim 2 , wherein said pain is chronic pain.