Phosphoramidites of the formula ##STR1## where R is a base-labile protecting group, R.sup.1 and R.sup.2 are individually alkyl of 1 to 6 carbon atoms, cycloalkyl of 3 to 8 carbon atoms, or aryl of 6 to 20 carbon atoms or are joined together to form with the nitrogen atom a cyclic structure of 4-7 carbon...http://www.google.com.au/patents/US5874552?utm_source=gb-gplus-sharePatent US5874552 - Modified phosphorous intermediates for providing functional groups on the 5' end of oligonucleotides
