Polysubstituted Oxygen Heterocycles by a Reformatsky-Type Reaction/Reductive Cyclization Approach from Enantiopure β-Ketosulfoxides
作者:Françoise Colobert、Sabine Choppin、Leticia Ferreiro-Mederos、Michel Obringer、Sandra Luengo Arratta、Antonio Urbano、M. Carmen Carreño
DOI:10.1021/ol701670g
日期:2007.10.1
The stereoselective synthesis of tetrasubstituted tetrahydrofurans and trisubstituted tetrahydropyrans bearing a sulfoxide was achieved by reductive cyclization (Et3SiH/TMSOTf) from the corresponding enantiopure hydroxy ketonesprotected as a dioxolane. These derivatives are easily accessible from a Reformatsky-type reaction between alpha-bromo-alpha'-sulfinyl ketones and protected alpha- or beta-ketoaldehydes
Reformatsky-Type Reaction of Chiral Nonracemic α-Bromo-α‘-sulfinyl Ketones with Aldehydes. Synthesis of Enantiomerically Pure 2-Methyl-1,3-diol Moieties
Chiral nonracemic alpha-bromo-alpha'-sulfinyl ketones were shown to react with aldehydes in the presence of SmI(2) in a Reformatsky-type reaction to give the corresponding adduct with excellent syn diastereoselectivity. Further reduction of the Reformatsky adducts furnished anti- and syn-2-methyl-1,3-diol moieties in excellent yields and diastereoselectivities.
SmI2-coupling reaction of chiral non-racemic α-bromo-α′-sulfinyl ketones with imines: synthesis of enantiomerically pure 2-methyl-3-amino-1-ol moieties
Chiral non-racemic alpha-bromo-alpha'-sulfinyl ketones were shown to react with imines in the presence of SmI2 to give the corresponding 1,3-aminoketo derivatives with good syn-diastereoselectivity. Further reduction of these adducts either with DIBAL-H only or with DIBAL-H in the presence of Yb(OTf)(3) afforded syn- and anti-2-methyl-3-amino-1-ol moieties, respectively, in good yields and diastereoselectivities. (C) 2009 Elsevier Ltd. All rights reserved.
Efficient and Stereoselective Access to the Polyol Fragment C9−C16 of Ansamycin Antibiotics
Efficient synthesis of the fragment C9−C16 bearing the anti,syn stereotriad of ansamycin antibiotics is described. Key steps for controlling the configuration of the three stereogenic centers involve a stereoselective Reformatsky-type reaction followed by a diastereoselective reduction of a β-ketosulfoxide.
sequence that involves a SmI2-promoted stereoselective Reformatsky addition of chiral nonracemic α-bromo α′-sulfinyl ketones to various aldehydes followed by stereoselective reduction of the Reformatsky adduct. The absolute configuration of the products was determined by comparison with literature data and by 1H NMR NOESY experiments. The observed stereoselectivities can be explained in terms of a boat