Strict Reagent Control in the Asymmetric Allylboration of N-TIPS-α-Amino Aldehydes with the B-Allyl-10-TMS-9-borabicyclo[3.3.2]decanes
摘要:
The allylboration of enantiomerically pure N-triisopropylsilyl-alpha-amino aldehydes (2) with B-allyl-10-trimethylsilyl-9-borabicyclo[3.3.2]decanes (1) proceeds cleanly at -78 degrees C, exhibiting essentially complete reagent control. After an oxidative workup, an HOAc-mediated N-->O TIPS rearrangement facilitates the clean formation of stable O-TIPS protected beta-amino alcohol derivatives 3 which are isolated in 60-83% yields in >= 96% de and >99% ee. For the leucinal series (R = i-Bu), an efficient entry to either statine (8aSS) or epi-statine (8aRS) is reported illustrating the versatility of this potent 1/2 combination.
Enantiomerically Pure α-Amino Aldehydes from Silylated α-Amino Acids
摘要:
The disilylation of alpha-amino acids 1 to provide 2 (72-87%) was achieved without racemization. An unprecedented borane-mediated semi-reduction strategy was devised to convert 2 to stable, isolable oxazaborolidines 3 (100%) which were hydrolyzed to provide 5 (49-60%) as pure, stable compounds. Analysis of the Mosher amides (8) of the gamma-amino esters 7 reveals that <= 2% racemization occurs in the 1 -> 8 conversions.
Enantiomerically Pure α-Amino Aldehydes from Silylated α-Amino Acids
作者:Buddy Soto-Cairoli、Jorge Justo de Pomar、John A. Soderquist
DOI:10.1021/ol7028993
日期:2008.1.1
The disilylation of alpha-amino acids 1 to provide 2 (72-87%) was achieved without racemization. An unprecedented borane-mediated semi-reduction strategy was devised to convert 2 to stable, isolable oxazaborolidines 3 (100%) which were hydrolyzed to provide 5 (49-60%) as pure, stable compounds. Analysis of the Mosher amides (8) of the gamma-amino esters 7 reveals that <= 2% racemization occurs in the 1 -> 8 conversions.
Strict Reagent Control in the Asymmetric Allylboration of <i>N</i>-TIPS-α-Amino Aldehydes with the <i>B-</i>Allyl-10-TMS-9-borabicyclo[3.3.2]decanes
作者:Buddy Soto-Cairoli、John A. Soderquist
DOI:10.1021/ol802685e
日期:2009.1.15
The allylboration of enantiomerically pure N-triisopropylsilyl-alpha-amino aldehydes (2) with B-allyl-10-trimethylsilyl-9-borabicyclo[3.3.2]decanes (1) proceeds cleanly at -78 degrees C, exhibiting essentially complete reagent control. After an oxidative workup, an HOAc-mediated N-->O TIPS rearrangement facilitates the clean formation of stable O-TIPS protected beta-amino alcohol derivatives 3 which are isolated in 60-83% yields in >= 96% de and >99% ee. For the leucinal series (R = i-Bu), an efficient entry to either statine (8aSS) or epi-statine (8aRS) is reported illustrating the versatility of this potent 1/2 combination.