A synthetic approach to poly(.gamma.-glutamyl) conjugates of methotrexate

Abstract

Methotrexate poly(gamma-L-glutamate)s bearing two and three glutamate units above that present in methotrexate have been synthesized by extension of a previously described route used to synthesize the lower conjugate bearing one added glutamate unit. Key steps in the sequence are the peptide coupling of N-[4-[[(benzyloxy)carbonyl]-methylamino]benzoyl]-L-glutamic acid alpha-benzyl ester (5) with oligo(gamma-L-glutamate) benzyl esters, removal of blocking groups by catalytic hydrogenolysis, and introduction of the (2,4-diamino-6-pteridinyl)methyl grouping by alkylation with 6-(bromomethyl)-2,4-pteridinediamine hydrobromide. Elaboration of the required oligo(gamma-L-glutamate) chain was achieved one unit at a time, beginning with the coupling of L-glutamic acid dibenzyl ester with [(tert-butyloxy)carbonyl]-L-glutamic acid alpha-benzyl ester (7), followed by selective removal of the tert-butyloxycarbonyl grouping and another coupling step with 5 or 7 as required. Diphenylphosphoryl azide was used as the coupling reagent in each conversion producing a peptide linkage.

Preparation of Multifunctional Fe@Au Core-Shell Nanoparticles with Surface Grafting as a Potential Treatment for Magnetic Hyperthermia

“…Methotrexate (MTX), a folic acid antagonist, is an effective anti-cancer therapeutic and immunologic agent [19]. Folic acid is an important precursor for metabolism.…”

Methotrexate-Modified Superparamagnetic Nanoparticles and Their Intracellular Uptake into Human Cancer Cells

“…However, despite the value of MTX in the treatment of cancers, target cells may develop resistance to this drug due to cellular efflux of the molecule . To counteract this phenomenon, researchers have developed MTX conjugates consisting of poly(glutamic acid) or poly(ethylene glycol) which retains a higher concentration of MTX within the cell. , These conjugates have been shown to increase cellular cytotoxicity and increase cellular mortality. Despite the success of these conjugates in vitro, there is still no clinical method of detecting the levels of MTX taken up by the target cells, which may reduce the efficacy of the treatment.…”

Synthesis of (6R)- and (6S)-5,10-dideazatetrahydrofolate oligo-γ-glutamates: Kinetics of multiple glutamate ligations catalyzed by folylpoly-γ-glutamate synthetase

“…Yield, 31%; k max (0.1 M NaOH)/nm 242 and 272; m/z (ESI + ) 573.2324 (M + H + . C 26 H 33 N 6 O 9 requires 573.2309) 574 (29%), 573 (100), 305 (50), 274 (22), and 261 (34); Ion-pair HPLC, t r = 20.8 min.…”