Frankiamide: A Structural Revision to Demethyl (C‐11) Cezomycin.

Abstract

Cezomycin. -The first calcimycin-class compound occurring in Frankia is revised from structure (Ia) to (Ib). -(KLIKA, K. D.; HAANSUU, J. P.; OVCHARENKO, V. V.; HAAHTELA, K. K.; VUORELA, P. M.; SILLANPAEAE, R.; PIHLAJA, K.; Z. Naturforsch., B: Chem.

Carbon–Carbon Bond Formation via Electron Transfer: Anodic Coupling

“…The corrected2 structure of 1 came with a formal absolute configuration opposite to that of 3 , although accompanied by a note that it “could not be ascertained to any degree of certainty”. After looking into all the available evidence for the absolute configurations for the pyrrol ether family, it appeared to us that this absolute configuration might be just as possible as that of 3 , although other publications unanimously presumed that the formal absolute configuration, like that of 3 , was correct.…”

“…When it was reported for the first time in 2001,1c this natural product was assigned a cyclic amide/imide structure ( 2 ) and was accordingly named frankiamide. However, subsequent single‐crystal X‐ray crystallographic analysis performed by the same authors reverted the structure from 2 to 1 with concurrent establishment of the relative configuration 2. A new trivial name was also given to reflect the corrected structure.…”

“… Demethyl (C‐11) cezomycin ( 1 , with the absolute configuration and atom numbering depicted as in Ref. 2), along with its initially assigned planar structure (frankiamide, 2 ) and several closely related natural spiroketals in the literature. …”

Structures and Properties of Naturally Occurring Polyether Antibiotics

“…Both compounds are isolated from the same strain as calcimycin. The crystal structure of cezomycin (Figure 9) was determined as its 11-demethyl complex with the sodium cation of the stoichiometry 2 : 1 [27]. …”

A Novel Allyl Transfer Coupled with a Grob Fragmentation

“…During our total synthesis of demethyl (C‐11) cezomycin, the most recent member in the pyrrol ether family of antibiotics, it was desired to remove the TBS protecting group in the intermediate 1 a to release a free OH group at the C‐6 position (Figure ). As the functionalities in this simple compound are not particularly unstable according to the existing knowledge, the desilylation was expected to be smooth and clean.…”