Backbone Modification using Ethyl Phosphoramidites


Applicable Products

2516 dT-Ethyl Phosphoramidite
2517 iBu-dG-Ethyl Phosphoramidite
2518 Bz-dA-Ethyl Phosphoramidite
2519 Bz-dC-Ethyl Phosphoramidite

Physical & Dilution Data

Dilution volumes (in ml) are for 0.1M solutions in dry acetonitrile (4050). Adjust accordingly for other concentrations. For µmol pack sizes, products should be diluted as 100µmol/ml to achieve 0.1M, regardless of molecular weight.


Mol. Formula

Mol. Wt.

Unit Wt.




2516 C39H50N3O8P 719.82 304.20 3.47 6.95 13.89
2517 C43H55N6O8P 814.92 329.21 3.07 6.14 12.27
2518 C46H53N6O7P 832.94 313.21 3.00 6.00 12.01
2519 C45H53N4O8P 808.91 289.18 3.09 6.18 12.36


A coupling time of 6min (360s) is recommended.

Cleavage & Deprotection

Assuming your strategy is to retain the ethyl groups, carry out deprotections at room temperature. Heating the oligos during deprotection will lead to loss of OEt from the phosphate backbone.

2516 & 2518 - Use ammonium hydroxide solution overnight at room temperature.

2517 - Use ammonium hydroxide solution at room temperature for 48h. Overnight deprotection does not completely remove the iBu nucleobase protection (~13% remains).

2519 - Use ammonium hydroxide solution overnight at room temperature. Note that deprotection with AMA will lead to transamination.

After deprotection remove the deprotection solution by G25. Do not heat the sample to remove deprotection reagents.

Storage & Stability

All phosphoramidites are stored refrigerated at a maximum of 2-8°C. Stability in solution is 2-3 days.


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