Total Synthesis and Absolute Stereochemical Assignment of Kibdelone C

Abstract

The kibdelones are hexacyclic tetrahydroxanthones and potent anticancer agents isolated from an Australian microbe. Herein, we describe the synthesis of a chiral, non-racemic iodocyclohexene carboxylate EF ring fragment of the kibdelones employing an intramolecular iodo halo-Michael aldol reaction and its merger with an ABCD ring fragment to afford the congener kibdelone C.

Total synthesis of clostrubin

“…The initial disassembly of the fully substituted B ring leads to a precursor 2 ; the recombination of the sterically hindered C8–C9 biaryl bond could rely on a 6π electrocyclization reaction. Electrocyclization has emerged as a powerful tool for the construction of fused ring systems since Nicolaou’s pioneering synthesis of endiandric acids 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 . In particular, the strategy of 6π electrocyclization/aromatization has demonstrated a significant advantage in the synthesis of multisubstituted arenes 33 34 35 36 37 38 39 40 41 42 43 44 .…”

Organocuprate‐Initiated Domino Michael–Intramolecular Aldol Reaction – Application to the Formation of Ring B of the Aglycon of Landomycins

“…Basically, this strategy requires conditions in which the highly reactive aldehyde function does not interfere with the first step of the process. Success has already been achieved with different heteroatom‐centered nucleophiles such as lithium tellurophenolate,5a or iodide 5c,5d. The synthetic usefulness of these transformations has been illustrated with an iodide‐triggered key cyclization en route to the synthesis of kibdelone C, as recently reported by the group of Porco 5d.…”

“…Success has already been achieved with different heteroatom‐centered nucleophiles such as lithium tellurophenolate,5a or iodide 5c,5d. The synthetic usefulness of these transformations has been illustrated with an iodide‐triggered key cyclization en route to the synthesis of kibdelone C, as recently reported by the group of Porco 5d. To the best of our knowledge, there is only one example with a carbon‐centered nucleophile : the group of Lu described the palladium‐catalyzed enantioselective cyclization of aryl boronic acids and salicylaldehyde butynoate 5b,8.…”

Albofungin and chloroalbofungin: antibiotic crystals with 2D but not 3D isostructurality

“…A search of the Cambridge Structural Database (CSD, Release 5.41; Groom et al, 2016) for the combined isoquinoline-xanthone skeleton found in 1 and 2 showed that relatively few related structures had been structurally determined previously and these are listed in Table 3. They include kigamicin A (Someno et al, 2005), simaomicin (Lee et al, 1989), kibdelone C methyl ether (Sloman et al, 2011a), lisolipin triacetate (Dobler & Keller-Schierlein, 1977), citreamicin " A (Liu et al, 2013) and the related Citreamccin sulfene adduct (Reich et al, 1993).…”