This paper describes the synthesis of the marine natural product, siphonarienal. The key step of this synthesis is an aldol reaction that constructs most of the skeleton and sets all three stereocenters of the target in one step from commercially available starting materials. Deoxygenation and chain homologation steps complete the synthesis.
Catalytic, Asymmetric Preparation of Ketene Dimers from Acid Chlorides
作者:Michael A. Calter、Robert K. Orr、Wei Song
DOI:10.1021/ol0359517
日期:2003.11.1
monosubstituted ketenes generated in situ from the reaction of acidchlorides and diisopropylethylamine yields ketene dimers in high yields and enantioselectivities. This reaction tolerates sterically demanding and functionally diverse substituents. Kinetic studies suggest that the rate-determining step for the reaction is the deprotonation of the acidchloride by the tertiary amine to form ketene and that the
Synthesis of the C21–C34-segment of the aplyronines using the dimer of methylketene
作者:Michael A Calter、Xin Guo
DOI:10.1016/s0040-4020(02)00723-8
日期:2002.8
This report describes a convergent synthesis of the C21–C34-segment of aplyronine. The starting point for both halves of this segment was the dimer of methylketene, readily available in either enantiomeric form by asymmetric catalysis. Diastereoselective reduction and functional group manipulation afforded the partners for a Wittig coupling reaction. The appropriate choice of oxygen protecting groups
Catalytic, Asymmetric Synthesis and Diastereoselective Aldol Reactions of Dipropionate Equivalents
作者:Michael A. Calter、Wei Song、Jianguang Zhou
DOI:10.1021/jo035668l
日期:2004.2.1
methylketene can be conveniently prepared in one step and high enantiomeric excess from propionyl chloride, using a catalytic amount of a silylated cinchona alkaloid as a source of chirality. Opening of the dimer with a lithiated sulfonamide affords a β-ketosulfonimide, which undergoes Sn(II)-mediated aldol reactions to diastereoselectively afford the anti,syn-aldol adduct. Alternatively, reduction of the dimer
One-Pot, Catalytic, Asymmetric Synthesis of Polypropionates
作者:Michael A. Calter、Xin Guo、Wensheng Liao
DOI:10.1021/ol015814e
日期:2001.5.1
[reaction: see text] The opening of methylketene dimer, followed by aldol reactions of the resulting enolate, provides a convenient access to syn,syn-dipropionate aldol adducts of a variety of aldehydes. These aldol adducts are usefulprecursors in the synthesis of complex polypropionates.
First Total Synthesis of a Natural Product Containing a Chiral, β-Diketone: Synthesis and Stereochemical Reassignment of Siphonarienedione and Siphonarienolone
作者:Michael A. Calter、Wensheng Liao
DOI:10.1021/ja027675h
日期:2002.11.1
siphonarienedione are described. The development of a stereoselective synthesis of beta-diketones facilitated the synthesis of the latter compound. The synthesis of the structures proposed for the natural products afforded compounds whose spectral data did not match those of the natural products. However, the synthesis of compounds isomeric to the proposed structures at C(4) and C(5) afforded compounds identical