We describe the characterisation of the O-methyltransferase JerF from the late stages of jerangolid biosynthesis. JerF is the first known example of an enzyme that catalyses the formation of a non-aromatic, cyclic methylenolether. The enzyme was overexpressed in E. coli and the cell-free extracts were used in bioconversion experiments. Chemical synthesis gave access to a series of substrate surrogates
作者:Paul T. O'Sullivan、Wilm Buhr、Mary Ann M. Fuhry、Justin R. Harrison、John E. Davies、Neil Feeder、David R. Marshall、Jonathan W. Burton、Andrew B. Holmes
DOI:10.1021/ja038353w
日期:2004.2.1
The totalsynthesis of octalactins A and B has been achieved in 15 steps (longest linear sequence) and 10% overall yield from commercially available materials. Key steps include the Paterson-Aldol reaction for the rapid assembly of the carbonate 46, methylenation of 46 and subsequent Claisen rearrangement of the corresponding alkenyl-substituted cyclic ketene acetal to provide the core unsaturated
八内酯 A 和 B 的全合成已通过 15 个步骤(最长的线性序列)和 10% 的市售材料总产率实现。关键步骤包括用于快速组装碳酸酯 46 的 Paterson-Aldol 反应、46 的亚甲基化和随后相应烯基取代的环烯酮缩醛的 Claisen 重排以提供核心不饱和中环内酯 47,以及使用酶-在中环内酯存在下介导的乙酸盐脱保护。
Lewis acid-catalyzed asymmetric hydroxymethylation of silicon enolates in aqueous media
Asymmetric hydroxymethylation of silicon enolates with formaldehyde in aqueousmedia has been achieved using praseodymium triflate and a chiral crown ether. Formaldehyde aqueous solution can be directly used for the reactions, and a water/THF mixture was found to be the best solvent system. This is the first example of catalytic asymmetric hydroxymethylation of silicon enolates.
Stereocontrolled Synthesis of 1,3-Diols from Enones: Cooperative Lewis Base-Mediated Intramolecular Carbonyl Hydrosilylations
作者:Casey Medina、Kyle P. Carter、Michael Miller、Timothy B. Clark、Gregory W. O’Neil
DOI:10.1021/jo401293a
日期:2013.9.20
A streamlined synthesis of beta-hydroxy ketone substrates has been developed to further investigate a recently discovered cooperative Lewis base-mediated intramolecular carbonyl hydrosilylation reaction. The synthesis features an enone beta-borylation/oxidation sequence that has proven to be quite general and high-yielding. This has allowed for additional investigations into the diastereoselectivity of the hydrosilylation reaction through the preparation of important polyketide fragments.
Direct Conversion of β-Hydroxyketones to Cyclic Disiloxanes
作者:Gregory W. O’Neil、Michael M. Miller、Kyle P. Carter
DOI:10.1021/ol1024635
日期:2010.11.19
beta-Hydroxyketones can be directly converted to cyclic disiloxanes using diphenylchlorosilane in the presence of imidazole and an amine base. The reaction is proposed to proceed via a nucleophilic activation mechanism through a cyclic chairlike transition state affording hydrosilylated products with high diastereoselectivity.