Synthesis of a Heterobifunctional PEG Spacer Terminated with Aminooxy and Bromide Functionality

Abstract

A simple and efficient synthesis of a novel heterobifunctional polyethylene glycol (PEG) spacer is described. The PEG spacer reagent is terminated with aminooxy and bromide functionality for ease of conjugation to a variety of electrophiles and/or nucleophiles.

heterobifunctional PEG - aminooxy - bioconjugation - molecular recognition - OEG - spacer

References and Notes

1

Present address: Department of Chemistry, University of Louisville, Louisville, KY 40292, USA

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19

For moisture-sensitive reactions, optimized yields were obtained only after drying the PEG intermediate by toluene azeotropic distillation immediately prior to use.

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22

¹H NMR and ¹³C NMR data (300 MHz and 75 MHz, respectively; in CDCl₃) for all compounds: Compound 1a: ¹H NMR: δ = 7.23 (br s, 1 H), 4.03 (m, 2 H), 3.82 (t, J = 6.3 Hz, 2 H), 3.74 (m, 2 H), 3.69 (app. s, 4 H), 3.48 (t, J = 6.3 Hz, 2 H), 1.48 (s, 9 H). ¹³C NMR: δ = 156.7, 81.7, 75.4, 71.2, 70.5, 70.4, 69.4, 30.2, 28.2.
Compound 1b: ¹H NMR: δ = 7.59 (br s, 1 H), 4.03 (m, 2 H), 3.82 (t, J = 6.3 Hz, 2 H), 3.70-3.66 (m, 8 H), 3.48 (t, J = 6.3 Hz, 2 H), 1.48 (s, 9 H). ¹³C NMR: δ = 156.7, 81.5, 75.3, 71.2, 70.6 (3 C), 70.5, 69.3, 30.2, 28.2.
Compound 3a: ¹H NMR: δ = 7.70-7.67 (m, 4 H), 7.44-7.35 (m, 6 H), 3.82 (t, J = 5.4 Hz, 2 H), 3.73-3.70 (m, 2 H), 3.66 (app. s, 4 H), 3.63 (m, 4 H), 2.17 (br s, 1 H), 1.05 (s. 9 H). ¹³C NMR: δ = 135.6, 133.6, 129.6, 127.6, 72.5, 70.8, 70.5, 63.4, 61.8, 26.8, 19.2.
Compound 3b: ¹H NMR: δ = 7.70-7.67 (m, 4 H), 7.44-7.35 (m, 6 H), 3.82 (t, J = 5.4 Hz, 2 H), 3.73-3.70 (m, 2 H), 3.66-3.58 (m, 12 H), 2.25 (br s, 1 H), 1.05 (s, 9 H). ¹³C NMR: δ = 135.6, 133.6, 129.6, 127.6, 72.5, 72.4, 70.7, 70.7, 70.4, 63.4, 61.8, 26.8, 19.2.
Compound 4a: ¹H NMR: δ = 7.83-7.80 (m, 2 H), 7.72-7.70 (m, 2 H), 7.70-7.65 (m, 4 H), 7.44-7.35 (m, 6 H), 4.36 (m, 2 H), 3.86 (m, 2 H), 3.74 (t, J = 5.4 Hz, 2 H), 3.65-3.62 (m, 2 H), 3.58-3.56 (m, 2 H), 3.52 (t, J = 5.4 Hz, 2 H), 1.03 (s, 9 H). ¹³C NMR: δ = 163.4, 135.6, 134.4, 133.7, 129.6, 129.0, 127.6, 123.4, 77.2, 72.4, 70.8, 70.7, 69.4, 63.3, 26.8, 19.2.
Compound 4b: ¹H NMR: δ = 7.84-7.81 (m, 2 H), 7.74-7.71 (m, 2 H), 7.70-7.66 (m, 4 H), 7.44-7.34 (m, 6 H), 4.36 (m, 2 H), 3.85 (m, 2 H), 3.79 (t, J = 5.4 Hz, 2 H), 3.67-3.63 (m, 2 H), 3.61-3.52 (m, 8 H), 1.04 (s, 9 H). ¹³C NMR: δ = 163.4, 135.6, 134.4, 133.7, 129.6, 129.0, 127.6, 77.2, 72.4, 70.8, 70.7, 70.6, 70.5, 69.3, 63.4, 26.8, 19.2.
Compound 5a: ¹H NMR: δ = 7.70-7.67 (m, 4 H), 7.44-7.35 (m, 6 H), 3.84 (m, 2 H), 3.81 (t, J = 5.4 Hz, 2 H), 3.69-3.59 (m, 8 H), 1.05 (s, 9 H). ¹³C NMR: δ = 135.6, 133.6, 129.6, 127.6, 74.7, 72.4, 70.7, 70.6, 69.7, 63.4, 26.8, 19.2.
Compound 5b: ¹H NMR: δ = 7.70-7.67 (m, 4 H), 7.44-7.35 (m, 6 H), 3.85 (m, 2 H), 3.81 (t, J = 5.4 Hz, 2 H), 3.69-3.63 (m, 10 H), 3.60 (t, J = 5.4 Hz, 2 H), 1.05 (s, 9 H). ¹³C NMR: δ = 135.6, 133.6, 129.6, 127.6, 74.6, 72.4, 70.7, 70.6, 70.5, 70.5, 69.7, 63.4, 26.8, 19.2.
Compound 6a: ¹H NMR: δ = 7.70-7.67 (m, 4 H), 7.51 (br s, 1 H), 7.44-7.34 (m, 6 H), 4.01 (m, 2 H), 3.82 (t, J = 5.4 Hz, 2 H), 3.72 (m, 2 H), 3.68-3.62 (m, 4 H), 3.61 (t, J = 5.4 Hz, 2 Hz), 1.46 (s, 9 H), 1.05 (s, 9 H). ¹³C NMR: δ = 156.7, 135.6, 133.6, 129.6, 127.6, 81.5, 75.3, 72.4, 70.7, 70.6, 69.4, 63.4, 28.2, 26.8, 19.2.
Compound 6b: ¹H NMR: δ = 7.70-7.67 (m, 4 H), 7.62 (br s, 1 H), 7.44-7.34 (m, 6 H), 4.01 (m, 2 H), 3.81 (t, J = 5.4 Hz, 2 H), 3.70 (m, 2 H), 3.67-3.62 (m, 8 H), 3.60 (t, J = 5.4 Hz, 2 H), 1.46 (s, 9 H), 1.05 (s, 9 H). ¹³C NMR: δ = 156.7, 135.6, 133.6, 129.6, 127.6, 81.4, 75.3, 72.3, 70.7, 70.6, 70.5, 70.5, 69.2, 63.4, 28.2, 26.8, 19.1.
Compound 7a: ¹H NMR: δ = 7.82 (br s, 1 H), 4.03 (m, 2 H), 3.76-3.72 (m, 4 H), 3.69 (s, 4 H), 3.64-3.61 (m, 4 H), 2.84 (br s, 1 H), 1.48 (s, 9 H). ¹³C NMR: δ = 156.8, 81.6, 75.2, 72.6, 70.4, 70.2, 69.2, 61.6, 28.2.
Compound 7b: ¹H NMR: δ = 8.08 (br s, 1 H), 4.02 (m, 2 H), 3.74-3.66 (m, 12 H), 3.63 (m, 2 H), 2.80 (br s, 1 H), 1.48 (s, 9 H). ¹³C NMR: δ = 156.9, 81.4, 75.1, 72.6, 70.6, 70.4, 70.4, 70.3, 69.0, 61.7, 28.2.

23 Gaertner HF. Offord RE. Bioconjugate Chem.  1996,  7:  38 

24

Compound 9 was obtained as a single isomer: ¹H NMR (600 MHz, CDCl₃): δ = 8.13 (s, 1 H), 7.58-7.57 (m, 2 H), 7.38-7.36 (m, 3 H), 4.34 (t, J = 4.6 Hz, 2 H), 3.83-3.81 (m, 4 H), 3.70 (app. s, 4 H), 3.46 (t, J = 6.0 Hz, 2 H). ¹³C NMR (75 MHz, CDCl₃): δ = 149.0, 132.2, 129.8, 128.7, 127.0, 73.5, 71.2, 70.7, 70.5, 69.7, 30.3.