Asymmetric γ-Methoxyallylation with the Robust 10-TMS-9-Borabicyclo[3.3.2]decanes
摘要:
The asymmetric gamma-methoxyallylboration of aldehydes with the configurationally very stable 1 gives nonracemic threo-beta-methoxyhomoallylic alcohols 7 (65-93%) with excellent selectivity (96-99% de, 98-99% ee). The corresponding homoallylic amines 10 are obtained from N-H aldimines with similar efficiency (72-96%) and with excellent diastereoselectivity (98% de) but with lower enantioselectivity (56-86% ee). These new reagents provide ready access to a Taxol side chain derivative.
1-aminophosphonic acids or reacted with Boc2O to yield N-Boc-protected 1-aminophosphonates. The enantiomers of 2-benzylthio-1-(t-butoxycarbonylamino)propylphosphonate were obtained from the racemate by chiral HPLC and converted to phosphonic acidanalogs of (R)- and (S)-homocysteine, (R)- and (S)-2-aminobutyric acid and (S)-methionine, all of ee >97% as determined by chiral HPLC.