Total Synthesis of (−)-Kendomycin Exploiting a Petasis−Ferrier Rearrangement/Ring-Closing Olefin Metathesis Synthetic Strategy

Step-wise and pre-organization induced synthesis of a crossed alkene-bridged nisin Z DE-ring mimic by ring-closing metathesis

This paper describes two approaches for the synthesis of a crossed alkene-bridged mimic of the thioether ring system of the nisin Z DE-fragment. The first approach comprised the stepwise total synthesis featuring a cross metathesis and a macrolactamization on a solid support followed by a ring-closing metathesis in solution. Via this route the title compound was obtained in an overall yield of 7% (85% on average for 16 reaction steps). In the second approach, the linear precursor peptide was subjected to ring-closing metathesis and the bicyclic peptide with the correct side chain connectivity pattern was obtained in yields up to 95%. The preferred formation of the bicyclic crossed alkene-bridged mimic of the DE-ring suggests a favorable pre-organization of the linear precursor peptide.

Total Synthesis of (±)-Pallavicinin and (±)-Neopallavicinin

Through a biomimetic pathway, (+/-)-pallavicinin and (+/-)-neopallavicinin were synthesized from (+/-)-Wieland-Miescher ketone via Grob fragmentation, intramolecular aldol cyclization, and intramolecular Michael reaction. The synthesis was stereocontrolled efficiently and followed the stereochemistry of the Wieland-Miescher ketone, and could provide opportunities for access to analogues of pallavicinin, neopallavicinin, and other related bioactive diterpenoids.

Evolution of a Total Synthesis of (−)-Kendomycin Exploiting a Petasis−Ferrier Rearrangement/Ring-Closing Olefin Metathesis Strategy

A convergent stereocontrolled total synthesis of (-)-kendomycin (1) has been achieved. The synthesis proceeds with a longest linear sequence of 21 steps, beginning with commercially available 2,4-dimethoxy-3-methylbenzaldehyde (12). Highlights of the synthesis include an effective Petasis-Ferrier union/rearrangement tactic to construct the sterically encumbered tetrahydropyran ring, a ring-closing metathesis to generate the C(4a-13-20a) macrocycle, an effective epoxidation/deoxygenation sequence to isomerize the C(13,14) olefin, and a biomimetic quinone-methide-lactol assembly to complete the synthesis.

Rapid stereocontrolled assembly of the fully substituted C-aryl glycoside of kendomycin with a Prins cyclization: a formal synthesis

Prins cyclization using an electron-rich benzaldehyde and a homoallylic alcohol efficiently delivered the fully substituted C-aryl tetrahydropyranoside of kendomycin.

Efforts toward the Total Synthesis of (−)-Kendomycin

[structure: see text] The synthesis of an advanced component leading to (-)-kendomycin is described. The synthetic scheme features the application of asymmetric conjugate addition methodology for the early generation of the C13-C14 (E)-trisubstituted olefin, providing an efficient assembly of the ansa chain. Condensation reactions probe two strategies for attachment of the aromatic system.