A compound having the formula: wherein: R 1 and R 2 represent radicals independently selected from the group consisting of hydrogen and C 1 - C 10 alkyl; R 3 and R 4 represent radicals independently selected from the group consisting of hydrogen and C 1 - C 10 alkyl; or R 3 and R 4 taken together with the carbons to which they are attached form a cyclic structure selected from the group consisting of wherein R 7, R 8, R 9, R 10, R 11, and R 12 represent radicals that are independently selected from the group consisting of hydrogen and C 1 - C 10 alkyl; R 5 represents a radical selected from the group consisting of hydrogen and C 1 - C 10 alkyl; R 6 represents a radical selected from the group consisting2 of straight- or branched chain C 1 - C 10 alkyl, C 3 - C 10 monocyclic cycloalkyl, C 7 - C 28 bicyclic or tricyclic cycloalkyl, cycloalkylalkyl, C 2 - C 7 alkenyl, C 2 - C 7 alkynyl, C 5 - C 10 monocyclic cycloalkenyl, C 7 - C 28 bicyclic or tricyclic cycloalkenyl, a substituted or unsubstituted C 6 - C 10 aryl group, a substituted or unsubstituted heteroaryl group selected from the group consisting of furyl, thienyl, pyridyl, pyrrolyl, oxazolyl, thiazolyl, imidazolyl, pyrazolyl, isoxazolyl, isothiazolyl, 1,2,3-oxadiazolyl, 1,2,3-triazolyl, and tetrazolyl; a substituted or unsubstituted arylalkyl group, and a substituted or unsubstituted heteroarylalkyl group, wherein the heteroaryl is selected from the group consisting of pyridine and thiophene; M is selected from the group consisting of, wherein R 13, R 14, R 15 and R 16 are independently selected from the group consisting of hydrogen and alkyl; said aryl group substituents and said arylalkyl group substituents being one or more radical(s) independently selected from the group consisting of a straight- or branched chain alkyl, alkoxy, alkoxyalkyl, alkoxyalkoxy, halogen, polyfluoroalkyl, polyfluoroalkoxy, carboxy, cyano, nitro, amido, amidoalkyl, amidino, carboxamide, alkylthio, alkylsulfinyl, alkylsulfonyl, sulfonamide, and mercapto; said heteroaryl group substituents and said heteroarylalkyl group substituents being one or more radical(s) independently selected from the group consisting of a straight- or branched chain alkyl, hydroxy, alkoxy, alkoxyalkyl, alkoxyalkoxy, halogen, polyfluoroalkyl, polyfluoroalkoxy, carboxy, cyano, amino, monoalkylamino, dialkylamino, aminoalkyl, nitro, amido, amidoalkyl, amidino, carboxamide, alkylthio, alkylsulfinyl, alkylsulfonyl, sulfonamide, and mercapto; or a pharmaceutically acceptable salt thereof, in a pharmaceutically acceptable amount for use in treatment or prophylaxis of an infection caused by an orthopox virus in a living host having or susceptible to said infection. R 1 and R 2 represent radicals independently selected from the group consisting of hydrogen and C 1 - C 10 alkyl; R 3 and R 4 represent radicals independently selected from the group consisting of hydrogen and C 1 - C 10 alkyl; or R 3 and R 4 taken together with the carbons to which they are attached form a cyclic structure selected from the group consisting of wherein R 7, R 8, R 9, R 10, R 11, and R 12 represent radicals that are independently selected from the group consisting of hydrogen and C 1 - C 10 alkyl; R 5 represents a radical selected from the group consisting of hydrogen and C 1 - C 10 alkyl; R 6 represents a radical selected from the group consisting2 of straight- or branched chain C 1 - C 10 alkyl, C 3 - C 10 monocyclic cycloalkyl, C 7 - C 28 bicyclic or tricyclic cycloalkyl, cycloalkylalkyl, C 2 - C 7 alkenyl, C 2 - C 7 alkynyl, C 5 - C 10 monocyclic cycloalkenyl, C 7 - C 28 bicyclic or tricyclic cycloalkenyl, a substituted or unsubstituted C 6 - C 10 aryl group, a substituted or unsubstituted heteroaryl group selected from the group consisting of furyl, thienyl, pyridyl, pyrrolyl, oxazolyl, thiazolyl, imidazolyl, pyrazolyl, isoxazolyl, isothiazolyl, 1,2,3-oxadiazolyl, 1,2,3-triazolyl, and tetrazolyl; a substituted or unsubstituted arylalkyl group, and a substituted or unsubstituted heteroarylalkyl group, wherein the heteroaryl is selected from the group consisting of pyridine and thiophene; M is selected from the group consisting of, wherein R 13, R 14, R 15 and R 16 are independently selected from the group consisting of hydrogen and alkyl; said aryl group substituents and said arylalkyl group substituents being one or more radical(s) independently selected from the group consisting of a straight- or branched chain alkyl, alkoxy, alkoxyalkyl, alkoxyalkoxy, halogen, polyfluoroalkyl, polyfluoroalkoxy, carboxy, cyano, nitro, amido, amidoalkyl, amidino, carboxamide, alkylthio, alkylsulfinyl, alkylsulfonyl, sulfonamide, and mercapto; said heteroaryl group substituents and said heteroarylalkyl group substituents being one or more radical(s) independently selected from the group consisting of a straight- or branched chain alkyl, hydroxy, alkoxy, alkoxyalkyl, alkoxyalkoxy, halogen, polyfluoroalkyl, polyfluoroalkoxy, carboxy, cyano, amino, monoalkylamino, dialkylamino, aminoalkyl, nitro, amido, amidoalkyl, amidino, carboxamide, alkylthio, alkylsulfinyl, alkylsulfonyl, sulfonamide, and mercapto;