(S)-4-Benzyl-2-oxazolidinone

Total Synthesis of Bryostatin 2

“…While some congeners ( 1b − d ) differ from bryostatin 1 ( 1a ) only in the acyl residues appended to the C 7 and C 20 hydroxyls, others (e.g., 1e and 2 ) embody significant changes in the C 19 −C 27 region of the bryostatin nucleus. Our interest in the synthesis of bryostatin was motivated by three circumstances: (i) the strict polyacetate origin of the bryostatin macrolides offered an ideal forum for the extension of our aldol-based approach to polypropionate natural products; (ii) the clinically relevant bryostatin 1 remains a scarce and expensive commodity; and (iii) simpler analogues might prove to be viable medicinal agents and useful biological probes. In this study, we describe the details of our synthesis of bryostatin 2 ( 1b ), a natural congener and synthetic precursor of 1a .…”

Diastereoselective Synthesis of Fused Lactone-Pyrrolidinones; Application to a Formal Synthesis of (−)-Salinosporamide A

“…The synthetic utility of the developed methodology was demonstrated by the enantioselective synthesis of the lactone-pyrrolidinone 24 , an intermediate in Danishefsky’s synthesis of the proteasome inhibitor (−)-salinosporamide A (Scheme ) . The known carboxylic acid 18 was readily prepared and converted into the allyl-substituted oxazolidinone 21 using an Evans asymmetric alkylation . Hydrolysis of the chiral auxiliary in 21 required initial conversion into the corresponding benzyl ester followed by in situ hydrolysis to the carboxylic acid so as to avoid endo cleavage of the oxazolidinone .…”

“…The known carboxylic acid 18 was readily prepared and converted into the allyl-substituted oxazolidinone 21 using an Evans asymmetric alkylation . Hydrolysis of the chiral auxiliary in 21 required initial conversion into the corresponding benzyl ester followed by in situ hydrolysis to the carboxylic acid so as to avoid endo cleavage of the oxazolidinone . The carboxylic acid was coupled with the amino malonate 22 under Schotten–Baumann conditions to give the amide 23 .…”

An Asymmetric Vinylogous Michael Cascade of Silyl Glyoximide, Vinyl Grignard, and Nitroalkenes via Long Range Stereoinduction

“…Compared to other vinylogous Michael methodologies, silyl glyoximides offer a conceptually distinct approach to the requisite dienolate nucleophile via a [1,2]-Brook rearrangement 20 that provides α-heteroatom functionality currently inaccessible through other methods (Scheme 1). The three-component coupling yields densely functionalized compounds, providing an enolsilane, nitro group, and acyl oxazolidinone 21 in the product.…”