The present invention provides a compound of the general formula Ia:wherein R2, R4, R5 are each independently selected of H, C(=O)R, C(=O)OR, P=O(OR)2, substituted or unsubstituted C1-C18 alkyl, substituted or unsubstituted C2-C18 alkenyl, substituted or unsubstituted C2-C18 alkynyl, substituted or unsubstituted arylwherein R1 is C(=O)R" or C(=O)OR", and R" is an optionally substituted alkyl with at least 4 carbon atoms or an optionally substituted alkenyl, wherein the optional substituents are selected from aryl or heterocyclic or R" is derived from an optionally protected amino acidwherein R6 and R7 are both =O and the dotted lines indicate a quinone ring, or R6 is -OR3, where R3 is H, C(=O)R, C(=O)OR substituted or unsubstituted C1-C18 alkyl, substituted or unsubstituted C2-C18 alkenyl, substituted or unsubstituted C2-C18 alkynyl, substituted or unsubstituted aryl, R7 is H, and the dotted lines indicate a phenyl ringwherein X2, X3, X4, X5, X6 are independently selected of H, OH, OR, SH, SR, SOR, SO2R, C(=O)R, C(=O)OR, NO2, NH2, NHR, N(R)2, NHC(=O)R, CN, halogen, substituted or unsubstituted C1-C24 alkyl, substituted or unsubstituted C2-C18 alkenyl, substituted or unsubstituted C2-C18 alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaromaticwherein X1 is independently selected of OH, CN, (=O), or Hwherein each of the R groups is independently selected from the group consisting of H, OH, NO2, NH2, SH, CN, halogen, C(=O)H, C(=O)CH3, CO2H, PO(OR)2, substituted or unsubstituted C1-C18 alkyl, substituted or unsubstituted C2-C18 alkenyl, substituted or unsubstituted C2-C18 alkynyl, substituted or unsubstituted arylwherein when R2, R3, R4, and R5 are substituted, the substituents are each independently selected from the group consisting of OH, OR, SH, SR, SOR, SO2R, C(=O)R, C(=O)OR, NO2, NH2, NHR, N(R)2, NHC(O)R, CN, halogen, =O, substituted or unsubstituted C1-C18 alkyl, substituted or unsubstituted C2-C18 alkenyl, substituted or unsubstitu
