Synthesis of the Sesquiterpenes Albicanol, Drimanol, and Drimanic Acid, and the Marine Sesquiterpene Hydroquinone Deoxyspongiaquinol

Abstract

A TiIII‐mediated radical cyclization cascade has been used for the synthesis of the sesquiterpenes (+)‐albicanol, (+)‐drimanol, and (+)‐drimanic acid. Starting from all‐trans‐farnesol, (+)‐albicanol could be prepared in seven steps in an overall yield of 14.9 %. Furthermore, a highly diastereoselective hydrogenation of (+)‐albicanol to give (+)‐drimanol has been developed. We used the synthesized (+)‐drimanic acid to achieve the first synthesis of the marine sesquiterpene hydroquinone deoxyspongiaquinol and the quinone deoxyspongiaquinone. Thus, this synthetic strategy gave access to five natural products.

Bioinspired synthesis of pentacyclic onocerane triterpenoids

“…Onoceranoxide 7 was formed from 10 via formation of the thiocarbamate and subsequent reduction with tributyltin hydride in 77% yield (2 steps) (2.0% overall yield starting from 16 ). 95 The spectroscopic data matched those reported in the literature. 26 …”

A Concise Route for the Synthesis of Tetracyclic Meroterpenoids: (±)-Aureol Preparation and Mechanistic Interpretation

“…Thus, the synthesis of (±)-aureol ((±)-1) from (±)-albicanol (5) was completed in only seven steps and a global 28% yield, substantially improving the synthetic procedures previously published [11][12][13][14][15][16][17][18][19][20]. Moreover, a simple epimerization of aureol (1) to 5-epi-aureol (11) has The synthesis of (±)-aureol ((±)-1) (Scheme 2) used as starting material (±)-albicanol (5), which was prepared through Cp 2 TiCl-catalyzed radical cascade cyclization of epoxy-farnesyl acetate, as previously reported by us and others [24,25]. Dess-Martin oxidation of 5 almost quantitatively afforded (±)-albicanal (6).…”

“…We thought the synthesis of 1 could be achieved through a coupling of albicanal (6) with 2lithiohydroquinone dimethyl ether and a biogenetic-type rearrangement (previously explored by us) as pivotal steps (Scheme 1). The synthesis of (±)-aureol ((±)-1) (Scheme 2) used as starting material (±)-albicanol (5), which was prepared through Cp2TiCl-catalyzed radical cascade cyclization of epoxy-farnesyl acetate, as previously reported by us and others [24,25]. Dess-Martin oxidation of 5 almost quantitatively afforded (±)-albicanal (6).…”

Syntheses of Combretastatins D-1, D-2, and D-4 via Ring Contraction by Flash Vacuum Pyrolysis

“…The latter was reduced quantitatively to the benzylalcohol 27 which was deacetylated with hydrazine to leave the thiol 28 in 94% yield. Finally, a new mild macrocyclization protocol employing SO 3 • pyridine 31 instead of sulfuric acid afforded the thioether 29 which was oxidized to the cyclic sulfone 30 with mCPBA. The mechanism of this process as well as the chemistry and potential chirality of such diaryl ether pentanoids (DAEP) remain to be elucidated.…”