Syntheses of the D-, E-, F-, and I-Ring Parts of Ciguatoxin by a Common Strategy Starting from Tri- O -acetyl- d -glucal

Abstract

Chiral medium-sized monocyclic ethers corresponding to the D-, E-, F-, and I-ring parts of ciguatoxin have been synthesized from tri-O-acetyl-D-glucal through a common synthetic route involving ring-closing olefin metathesis.

Enantioselective Total Synthesis of Brevetoxin A: Unified Strategy for the B, E, G, and J Subunits

“…The Crabtree catalyst proved remarkably effective for the reduction of the trisubstituted olefin of oxocene 43 ,20 providing the oxocane 44 and its C6 epimer in a 3:1 ratio at 25 °C, an 8:1 ratio at −20 °C and a >19:1 ratio (93 % yield) at −50 °C. The allylic hydroxyl effectively directs the hydrogenation of the C6–C7 alkene to the opposite face of the ring 19. Similar effects are observed in the directed Simmons–Smith cyclopropanation and directed epoxidation of cyclooctenol 24.…”

“…Reduction of the chiral auxiliary and formation of the cyclohexylidene acetal provided diene 29 . With the cyclic constraint in place, RCM8a,b provided oxocene 30 in 83 % yield 19. Replacement of the benzyl ether with a tert ‐butyldimethylsilyl ether that would be compatible with the reduction of the olefin was accomplished in two straightforward operations.…”

Synthesis of Natural Products Containing Medium‐Size Oxygen Heterocycles by Ring‐Closing Alkene Metathesis

“…By Fujiwara and Murai have used tri-O-acetyl-d-glucal as a precursor to both the ciguatoxin F-ring and the I-ring oxocine [53]. The coupling of aldehyde 230 with vinyl lithium gave 231 (Scheme 3.45).…”

“…A related sequence of reactions was used to generate the ciguatoxin F-ring oxonene as illustrated in Scheme 3.46 [53]. RCM using [Ru]-I catalyst gave oxonene 241 in 98% yield.…”

The chemistry of the carbon–transition metal double and triple bond: annual survey covering the year 2002

“…104) using Grubbs catalyst II pretreated with hydrogen [326]; (15) asymmetric formation of oxygen heterocycles using a chiral molybdenum carbene complex catalyst [327]; (16) formation of six-to nine-membered ring oxygen heterocycles for total synthesis of ciguatoxin and related compounds (e.g. 105, 106) [328][329][330][331][332][333][334][335][336][337][338]; (17) synthesis of various ␣,␤-unsaturated oxacyclic ketone derivatives [339]; (18) synthesis of various oxacycles fused to aromatic rings (e.g. 107) [340][341][342][343][344]; (19) synthesis of eight-membered ring cyclic lactones (e.g.…”