2-Ethoxy-1-(ethoxycarbonyl)-1,2-dihydroquinoline → Fmoc-Lys(MMT) valinol

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Reaction Steps

The synthesis is schematically shown in Scheme-2. L-Valinol (40 mg) was reacted with commercially available Fmoc-Lys(MMT)-OH (253 mg) and EEDQ (107 mg) in 10 mL of anhydrous dichloromethane at ambient temperature, under argon, for 3 h. Extractive work up followed by flash chromatography furnished the product Fmoc-Lys(MMT)-valinol as a pale yellow liquid (200 mg; ˜70% yield). HPLC: tR 14.38 min; electrospray mass spectrum: M+H: m/z 727. This intermediate (200 mg) was deprotected with diethylamine (10 mL), and the product (135 mg) was obtained in ˜90% purity after flash chromatography. HPLC: tR 10.91 min; electrospray mass spectrum: M+Na at m/z 527. This product (135 mg) was coupled with the commercially available O-(2-azidoethyl)-O′—(N-diglycolyl-2-aminoethyl)heptaethyleneglycol (‘PEG-N3’; 150 mg, 1.1 equiv.) in presence of EEDQ (72 mg, 1.1 equiv.) in 10 mL of dichloromethane, and stirred overnight at ambient temperature. The crude material was purified by flash chromatography to obtain 240 mg of the purified product as a light yellow oil (˜87% yield). HPLC: tR 11.55 min; electrospray mass spectrum: M+H and M+Na at m/z 1041 and 1063, respectively.

Provenance & Evidence