Vance O. Kennedy

Stereocontrolled 1,3-dipolar cycloadditions using Oppolzer's camphor sultam as the chiral auxiliary for carbonyl stabilized azomethine ylides

Abstract Two complementary approaches to substituted pyrrolidines via stereocontrolled 1,3-dipolar cycloaddition reactions of chiral azomethine ylides are described. In one approach, chiral azomethine ylides were generated by thermolysis of aziridine carboxylate sultams and trapped with a variety of dipolarophiles to give good yields of the corresponding cycloadducts. In the second approach, chiral azomethine ylides were generated from glycyl sultams by ‘imine tautomerization’ and trapped with dipolarophiles to give good yields of the corresponding cycloadducts.

STEREOCONTROLLED AND ENANTIOSELECTIVE SYNTHESIS OF THE BRANCHED 6-AMINO-4,6 -DEOXYHEPTOPYRANURONIC ACID COMPONENT OF AMIPURIMYCIN

Abstract A stereocontrolled and enantioselective synthesis of the branched 6-amino-4,6-deoxyheptopyranuronic acid component of amipurimycin is reported. Key stages in the synthesis include the stereodivergent assembly of the dihydropyrones 12 and 14 from serinal derivatives (S)-10 and (R)-10, elaboration of the tetrahydropyran ring to give 26 and 31, and finally, introduction of the cis-2-aminocyclopentanecarboxylic acid moiety to produce the diastereomeric peptides 28 29 and 32 33 .

Silane Dehydrocoupling Reactions Catalyzed by the Late Transition Metals

Synthesis of oligomeric silanes via homogeneous late transition metal catalyzed dehydrocoupling of silanes is discussed. We have found that primary silanes are converted to oligomeric silanes by platinum catalysts. We have isolated platinum-silicon four-membered rings (4MR) with short Si−Si cross ring contacts from these catalytic mixtures and find that the 4MR are catalysts for the oligomerization. The platinum-silicon 4MR have been fully characterized. The possible involvement of metal disilene complexes in the oligomerization process is discussed.