Stereoselective Synthesis ofRP- andSP-Dithymidine Phosphorothioates via Chiral Indolooxazaphosphorine Intermediates Derived from Tryptophan

A chiral auxiliary 1 and its enantiomer, which are easily prepared from L- and D-tryptophan, facilitate diastereoselective syntheses of phosphorothioate oligonucleotides. Phosphorothioate 2 was obtained from 1 in five steps with over 95 % de, and the enantiomer of 1 afforded (SP) -2 with an equally good de value. T=thymine residue. Supporting information for this article is available on the WWW under http: //www. wiley-vch. de/contents/jc₂002/2000/z15468ₛ. pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.