Saponin derivatives as adjuvants and photoaffinity probes

A compound of general formula (I) or a pharmaceutically acceptable salt thereof:

• wherein G is a branched trisacchride of formula (VI) or a stereoisomer of formula (VI)
• wherein each occurrence of RP is independently hydrogen or ORq;
• wherein each occurrence of Rq is independently hydrogen or an optionally substituted group selected from 6-10-membered aryl, benzyl, C1-6 aliphatic, or C1-6 heteroaliphatic having 1-2 heteroatoms independently selected from the group consisting of nitrogen, oxygen, and sulfur;
• or two Rq are taken together to form a 5-7-membered heterocyclic ring having 1-2 heteroatoms independently selected from the group consisting of nitrogen, oxygen, and sulfur;
• is a single or double bond;
• U is —CH3, —CH2—OH, —C═O or —CH═NOH;
• V is H or ORx;
• wherein Rx is independently hydrogen or an oxygen protecting group selected from the group consisting of alkyl ethers, benzyl ethers, silyl ethers, acetals, ketals, esters, carbamates, and carbonates;
• PRG is a moiety comprising a photoreactive group selected from diazirine, benzophenone azido or a combination thereof;
• Linker is a chemical spacer;
• and
• Biotin is a biotin moiety.