Enantioselective Construction of Vicinal Stereogenic Quaternary Centers by Dialkylation: Practical Total Syntheses of (+)- and meso-Chimonanthine

All three stereoisomers of the hexacyclic 3a,3a'-bispyrrolidino[2,3-b]indoline moiety found in complex indole alkaloids can be prepared, as illustrated by total syntheses of meso-chimonanthine (1) and (+)-chimonanthine (2). A rare example of high diastereoselectivity arising from the combination of a prostereogenic enolate with a chiral electrophile containing a sp(3) carbon atom is the key feature of the asymmetric synthesis of the C(2) stereoisomer.     

Total synthesis of the supposed structure of (-)-sclerophytin A and an improved route to (-)-7-deacetoxyalcyonin acetate

[reaction: see text]Stereoselective acid-catalyzed rearrangement of 15-->16 is the central step in total syntheses of (-)-7-deacetoxyalcyonin acetate (1) and the compound with the alleged structure of sclerophytin A (2). Since tetracyclic diether 2 is not identical to sclerophytin A, the structure of this antineoplastic marine diterpene must be revised. The conversion of 15-->16 demonstrates for the first time that tetrahydrofurans containing (Z)-1-methylalkenyl side chains can be prepared by Prins-pinacol rearrangements.     

Untersuchung von Milch und Molkereiprodukten

Ohne Zusammenfassung     

Diastereoselective Coupling of Chiral Acetonide Trisubstituted Radicals with Alkenes

The stereochemical outcome of reactions of chiral nucleophilic trisubstituted acetonide radicals with electron‐deficient alkenes is dictated by a delicate balance between destabilizing non‐bonding interactions and stabilizing hydrogen‐bonding between substituents on the α and β carbons.