Studies for the Synthesis of Xenicane Diterpenes. A Stereocontrolled Total Synthesis of 4-Hydroxydictyolactone

Abstract

The stereocontrolled total synthesis of 4-hydroxydictyolactone (4), a member of the xenicane diterpene family of natural products, is described. These studies feature the development of the B-alkyl Suzuki cross-coupling reaction for direct access to (E)-cyclononenes from acyclic precursors. The Ireland-Claisen rearrangement is effectively utilized to establish the backbone asymmetry of the contiguous C2, C3, C10 stereotriad of 4. The synthesis strategy has devised an intramolecular Nozaki-Hiyama reductive allylation of a formate ester for the stereoselective formation of five-membered lactols 22. In addition, an internally directed SE' propargylation using allenylmagnesium bromide is described to establish the stereochemistry of the C4 alcohol in 27, and the terminal alkyne is subsequently functionalized via a regioselective syn-silylstannylation to yield 30. Finally, the stereocontrolled phenylselenylation of the ester enolate derived from 43 leads to the desired syn-oxidative elimination to yield the natural product 4.

Advances in Transition Metal (Pd,Ni,Fe)-Catalyzed Cross-Coupling Reactions Using Alkyl-organometallics as Reaction Partners

“…497 They utilized a cross-coupling protocol to construct a macrocycle from highly functionalized late stage intermediate 173 . During their optimization, they observed a significant influence of the protecting group on the reaction outcome.…”

Marine natural products

“…349 This same alga was also the source of the cadinane sesquiterpenes 306 and 307, and six other known cadinanes. 355 The inhibitory activity of two known dolastanes from Dictyota cericornis (Baia da Ribeira, Brazil) against mammalian Na + K + -ATPase was evaluated. 352 In a study of a Mediterranean Dictyota sp.…”

Evolution of a Unified Strategy for Complex Sesterterpenoids: Progress toward Astellatol and the Total Synthesis of (−)‐Nitidasin

“…Consequentially,w ea ssumed that the alcohol might be too burdened in its steric environmentt o affect the envisaged transformation. Indeed, exposing alkyne 65 to Bu 3 SnSiMe 3 under Pd catalysis gave rise to as ingle regioisomer 66.S ubsequent iododestannylation( I 2 ,2 ,6-di-tert-butyl-4-methylpyridine, À40 8C) [66] and treatment with Me 2 CuLi delivered alkenyl silane 67.T oaccess the macrocyclization precursor 60,w et reated silane 67 with excess N-iodosuccinimide (NIS) ( % 2.5 equivalents) in MeCN to affect an iododesilylation. Upon isolation of an ew product, 1 HNMR spectroscopy revealed that the iododesilylation took place as indicated by ad ownfield shift of the alkenyl proton from d = 5.20 to 5.89 ppm.…”