Abstract: A compound with formula (I) where R10 is a therapeutically removable nitrogen protecting group; R2 and R3 are independently selected from: H, R, OH, OR, ═O, ═CH—R, ═CH2, CH2—CO2R, CH2—CO2H, CH2—SO2R, O—SO2—R, CO2R, COR and CN; R6, R7 and R9 are independently selected from H, R, OH, OR, halo, amino, nitro, Me3Sn; X is S, O or NH; R11 is either H or R; and where there is optionally a double bond between C1 and C2 or C2 and C3; and R8 is selected from H, R, OH, OR, halo, amino, nitro, Me3Sn, or R7 and R8 together form a group —O—(CH2)p—O—, where p is 1 or 2. Such compounds may be used in methods of ADEPT, GDEPT, NPEPT or PDT.