PubMed · 11341163
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K C Nicolaou, C N Boddy. 2001. Behind enemy lines.. https://doi.org/10.1038/scientificamerican0501-54
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The intramolecular Diels-Alder reaction of N-3,5-hexadienoyl ethyl acrylimidates provides an efficient method for the synthesis of cis-fused hexahydroisoquinolones. As a demonstration of the stereochemical control offered by this cycloaddition, two approaches to the construction of the DE rings of reserpine are reported. In the second entry, N-((4-(trimethylsilyl)ethoxymethoxy)methyl-6-benzyloxy-3Z,5E-hexadienoyl)-1-aza-2-ethoxy-1,3-butadiene (40) undergoes cycloaddition to produce as the major product (4aS,7R,8aS)-7-benzyloxy-5-((2-trimethylsilyl)ethoxymethoxy)methyl-3,4,4a,7,8,8a-hexahydroisoquinol-3-one (41). Cycloadduct 41 is then stereospecifically elaborated to (4aS,5S,6R,7R,8aR)-6-methoxy-5-methoxycarbonyl-7-(3,4,5-trimethoxy)benzoyldecahydroisoquinoline-2-carboxylic acid methyl ester (3), a key intermediate previously transformed to reserpine.
A novel, efficient, and stereoselective synthesis of fragment A of cryptophycin 3 is disclosed. The key step involves the regio- and stereoselective transformation of an unsaturated ester to a bromohydrin via anchimeric assistance by the sulfinyl group.
The synthesis of a small library of differentially-linked beta-C-disaccharides has been carried out through the use of a radical allylation-RCM strategy. Acids 6 were prepared by Keck allylation of a suitable carbohydrate-based radical precursor, followed by oxidative cleavage of the formed alkene. Dehydrative coupling of these acids with the known olefin alcohol 5 then gave the precursor esters 7 in excellent yield. Methylenation of the esters 7 was followed by RCM and in situ hydroboration-oxidation of the formed glycals to furnish the protected beta-C-disaccharides 10 in good overall yield. Five examples were then deprotected and screened for their efficacy as enzyme inhibitors of beta-glycosidase and against several solid-tumor cell lines for in vitro differential cytotoxicity.