Design and synthesis of water-soluble bioconjugatable trans-AB-porphyrins

Abstract

Three free base porphyrins have been prepared that bear a polar and facially encumbering 2,4,6-tris(carboxymethoxy)phenyl motif at one meso (5-) position. The only other substituent (15-position) comprises phenyl, formyl, or p-aminophenyl. The porphyrins exhibit solubility in water (or aqueous buffer solutions) at pH >/=7 and concentrations >1 mM at room temperature. The concise syntheses, water-solubility, and bioconjugatable handle make these porphyrin constructs suitable for biological applications.

Figure 1

Molecular model of porphyrin H₂P-1 showing conformations (not energy-minimized) of the 2,6-carboxymethoxy units attached to the aryl moiety.

Figure 2

Variable temperature ¹H NMR spectra for porphyrin H₂P-2 in DMSO-d₆.

Figure 3

Absorption spectra of porphyrin H₂P-3 at room temperature in water (solid line), THF (dashed line) and DMSO (dotted line).

Figure 4

Absorption spectra of porphyrins in aqueous buffer solution (pH = 7) at room temperature as a function of concentration. (A) Porphyrin H₂P-1: (solid line) c = 2.8 mM, l = 1 mm; (dotted line) c = 0.56 mM, l = 5 mm; (dashed line) c = 0.28 mM, l = 10 mm. (B) Porphyrin H₂P-2: (solid line) c = 2.5 mM, l = 1 mm; (dotted line) c = 0.5 mM, l = 5 mm; (dashed line) c = 0.25 mM, l = 10 mm. (C) Porphyrin H₂P-3: (solid line) c = 3 mM, l = 1 mm; (dotted line) c = 0.6 mM, l = 5 mm; (dashed line) c = 0.3 mM, l = 10 mm.

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