Oxygenated and amino- or ammonium-containing phosphonic acid derivatives and their medical use

A compound of formula 1 or a pharmaceutically acceptable salt, solvate or prodrug thereof,

• wherein:
• R1 is a C10-20 hydrocarbon group;
• R2 and R3 are mutually linked to form a pyrrolidine ring, a piperidine ring or an azepane ring together with the nitrogen atom X to which they are attached, wherein said pyrrolidine ring, said piperidine ring or said azepane ring is optionally substituted with one or more groups independently selected from —OH, —O(C1-3 alkyl), —O—C(O)—(C1-3 alkyl), C1-3 alkyl, —NH2, —NH(C1-3 alkyl) or —N(C1-3 alkyl)(C1-3 alkyl);
• R4 is a C3-6 alkylene group which is substituted with one or more groups independently selected from —OH, —O(C1-3 alkyl), —O—C(O)—(C1-3 alkyl), —O—C(O)—O(C1-3 alkyl), —O—C(O)—NH2, —O—C(O)—NH(C1-3 alkyl), —O—C(O)—N(C1-3 alkyl)(C1-3 alkyl), —O(CH2)2OH or —O(CH2)3OH;
• R5 is —PO3H−, —PO32−, —PO3H2, —PO2(OC1-3 alkyl), —PO2H(OC1-3 alkyl), or —PO(OC1-3 alkyl)2;
• and
• X is N+.