Efficient and stereoselective access to the polyol fragment C9-C16 of ansamycin antibiotics
Image Persented Efficient synthesis of the fragment C9-C16 bearing the anti, syn stereotriad of ansamycin antibiotics is described. Key steps for controlling the configuration of the three stereogenic centers involve a stereoselective Reformatsky-type reaction followed by a diastereoselective reduction of a β-ketosulfoxide.
Switchover of diastereofacial selectivity in the condensation reaction of optically active N-sulfinimine with ester enolate
Both diastereomers of β-aminoester can be obtained diastereoselectively in the reaction of optically active N-sulfinimine possessing 2-methyl-1,3- dioxolanyl group with ester enolate simply by changing the enolate metal species, additives, and solvents. The β-aminoester can be converted into the corresponding 3-unsubstituted β-lactam.