Dealkylation of phosphonate esters
and subsequent tert-butyl deprotection of NODA-GA
tris(tBu)3-conjugate11 (9.0 mg, 5.1 μmol, 1.00 equiv) were performed with
trimethylsilyl bromide (8.1 μL, 66.8 μmol, 13.0 equiv)
and 400 μL of the deprotection cocktail, respectively, according
to GP-5. Semipreparative RP-HPLC purification [Agilent Zorbax SB C-18
5 μm 80 Å, 9.4 × 250 mm with 20–80% acetonitrile
(0.1% TFA) in water (0.1% TFA) in a linear gradient over 45 min, 6
mL/min, Rt = 12 min] and subsequent lyophilization
yielded the NODA-GA-conjugate11 (4.6 mg, 3.0 μmol,
57% over two steps) as a colorless powder. mp 215 °C (decomposition). Rt = 15.88 min (system B), purity = 100%. IR
(ATR): ṽ 1650 (m), 1573 (w), 1502 (w), 1451
(w), 1408 (w), 1305 (m), 1145 (s), 1036 (m), 768 (w), 719 cm–1 (w). MS (HR-ESI+): exact mass calculated for [M + H]+: m/z 1528.4472, measured: m/z 1528.4458.
and subsequent tert-butyl deprotection of NODA-GA
tris(tBu)3-conjugate
trimethylsilyl bromide (8.1 μL, 66.8 μmol, 13.0 equiv)
and 400 μL of the deprotection cocktail, respectively, according
to GP-5. Semipreparative RP-HPLC purification [Agilent Zorbax SB C-18
5 μm 80 Å, 9.4 × 250 mm with 20–80% acetonitrile
(0.1% TFA) in water (0.1% TFA) in a linear gradient over 45 min, 6
mL/min, Rt = 12 min] and subsequent lyophilization
yielded the NODA-GA-conjugate
57% over two steps) as a colorless powder. mp 215 °C (decomposition). Rt = 15.88 min (system B), purity = 100%. IR
(ATR): ṽ 1650 (m), 1573 (w), 1502 (w), 1451
(w), 1408 (w), 1305 (m), 1145 (s), 1036 (m), 768 (w), 719 cm–1 (w). MS (HR-ESI+): exact mass calculated for [M + H]+: m/z 1528.4472, measured: m/z 1528.4458.