70960-99-5Relevant articles and documents
Asymmetric total synthesis of ent-(-)-roseophilin: Assignment of absolute configuration
Boger,Hong
, p. 8515 - 8519 (2007/10/03)
An asymmetric total synthesis of ent-(-)-roseophilin (1), the unnatural enantiomer of a novel naturally occurring antitumor antibiotic, is described. The approach enlists a room temperature heterocyclic azadiene inverse electron demand Diels-Alder reaction of dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate (7) with the optically active enol ether 6 bearing the C23 chiral center followed by a reductive ring contraction reaction for formation of an appropriately functionalized pyrrole ring in a key 1,2,4,5-tetrazine → 1,2-diazine → pyrrole reaction sequence. A Grubbs' ring closing metathesis reaction was utilized to close the unusual 13-membered macrocycle prior to a subsequent 5-exo-trig acyl radical-alkene cyclization that was used to introduce the fused cyclopentanone and complete the preparation of the tricylic ansa-bridged azafulvene core 32. Condensation of 32 with 33 under the modified conditions of Tius and Harrington followed by final deprotection provided (22S,23S)-1. Comparison of synthetic (22S,23S)-1 ([α]25D, CD) with natural 1 established that they were enantiomers and enabled the assignment of the absolute stereochemistry of the natural product as 22R,23R. Surprisingly, ent-(-)-1 was found to be 2-10-fold more potent than natural (+)-1 in cytotoxic assays, providing ah unusually rewarding culmination to synthetic efforts that provided the unnatural enantiomer.
Palladium-Assisted N-Alkylation of Indoles: Attempted Application to Polycyclization
Hegedus, Louis S.,Winton, Peter M.,Varaprath Sudarsanan
, p. 2215 - 2221 (2007/10/02)
The palladium(II) complexes of the olefins ethene, propene, and 1-hexene reacted with 1-lithioindole to produce N-alkylated indoles exclusively.Attempts to perform this N-alkylation intramoleculary (to form tricyclic material from 2-allylskatole) failed.Anilines with dienic side chains in the 2-position were subjected to Pd(II)-assisted cyclization conditions in attempts to induce polycyclization.However, only monocyclization was observed.
