For 5′-attachment, we have found 5′-Cholesterol-CE Phosphoramidite (LK2170) to offer specific advantages in oligo synthesis. Since the cholesterol is attached directly to aminohexanol, it is not susceptible to 1,2-diol elimination as observed in some other products. Lack of a trityl group simplifies purification; some cholesterol products must be used in trityl-on mode (to prevent 1,2-diol elimination during deprotection), then detritylated, and can subsequently be very difficult to purify. Similarly, 5′-Cholesterol-TEG-CE Phosphoramidite (LK2189) is a simple 5′-modifier without the complications of a 1,2-diol and trityl protection, but with the added benefit of solubility in acetonitrile conferred by the TEG spacer.