Stereocontrolled aldol additions to α-methylene-β-alkoxy aldehydes: Application to the synthesis of a C13C25 segment of bafilomycin A1
摘要:
A boron-mediated, syn-aldol coupling between ethyl ketone 8 and aldehyde 9, followed by directed hydrogenation at C-16 and acetonide hydrolysis, gives the C-13-C-25 segment 6 of bafilomycin A(1).
Studies in polypropionate synthesis: High π-face selectivity in syn and anti aldol reactions of chiral boron enolates of lactate-derived ketones
摘要:
Use of (c)Hex(2)BCl/Me(2)NEt in the aldol reactions of the alpha'-benzoyloxy ketone 7 with aldehydes leads to high stereoselectivity (97-99.5% ds) for the crystalline anti adducts 11. Under similar conditions, the corresponding benzyl ether 6 favours formation of the syn adducts 9.
Manipulation of the aldol adducts from lactate-derived ketones. A versatile chiral auxiliary for the asymmetric synthesis of β-hydroxy carbonyl compounds
作者:Ian Paterson、Debra J. Wallace
DOI:10.1016/0040-4039(94)88435-8
日期:1994.11
The ketones 1 and 2 can be transformed into a wide range of enantiomerically-pure anti and syn α-methyl-β-hydroxy ketones and aldehydes. The α′-methyl group in 5 and 11 may be retained, demonstrating the use of the lactate-derived group as an optional chiral auxiliary.
Polyketide Synthesis Using the Boron-Mediated, anti-Aldol Reactions of Lactate-Derived Ketones: Total Synthesis of (-)-ACRL Toxin IIIB
作者:Ian Paterson
DOI:10.1055/s-1998-5929
日期:1998.3
The boron-mediated, anti-selective, aldol reactions of ketone 2 (and related derivatives) proceed with high levels of asymmetric induction, diastereoselectivities of up to 200:1 in favour of the aldol adducts 4 are obtained with achiral aldehydes and reagent control operates with chiral aldehydes. These lactate-derived ketones provide a versatile chiral auxiliary for the synthesis of beta-hydroxy carbonyl compounds. Oxidative removal of the auxiliary provides enantiomerically pure aldehydes 5, while reductive deoxygenation gives the corresponding ethyl ketones 6. This practical asymmetric methodology for generating anti-aldols is illustrated by an efficient total synthesis of (-)-ACRL toxin IIIB (7), which proceeds in 15 steps from 2 with 21% overall yield and 88% diastereoselectivity.
A Retro-Claisen Approach to Dolabriferol
作者:Troy Lister、Michael V. Perkins
DOI:10.1021/ol060347s
日期:2006.4.1
The protected precursor 30 to dolabriferol was generated by a DBU-induced, ester-forming, retro-Claisen process. The required linear carbon chain present in 22 was synthesized by a stereoselective lithium aldol reaction. The necessary aldehyde and ketone fragments were synthesized using stereocontrolled aldol reactions with the ethyl (S)-lactate derived ketone 13.