Enantioselective Synthesis of (+)-Royleanone from Sulfinyl Quinones

Abstract

A convergent enantioselective synthesis of (+)-royleanone (1) is described starting from enantiomerically pure (S)-3-hydroxy-2-isopropyl-5-tert-butylsulfinyl-p-benzoquinone, which is readily available from 3-isopropyl-1,2,4-trimethoxybenzene and 1,3,3-trimethyl-2-vinylcyclohexene. The key step is a tandem asymmetric Diels-Alder reaction/pyrolytic sulfoxide elimination process.

Regioselective Benzylic Oxidation of Aromatic Abietanes: Application to the Semisynthesis of the Naturally Occurring Picealactones A, B and C

“…Oxygenated aromatic abietanes at positions 7 and 15 exist widely in nature and display important biological activities including, for instance, the 7‐oxo compounds sugiol and salvinolone, the 7‐hydroxy aquilarabietic acids, the 7,20‐lactone carnosol or the 15‐hydroxy compound angustanoic acid F. Like many other natural products, they are usually not available in large amounts from nature and their difficult and expensive isolation greatly hampers the exploration of their medicinal potential . Instead their semisynthetic preparation is possible from commercially available abietanes including abietic, dehydroabietic and podocarpic acids, which are oxidized at positions 7 and 15, or by total synthesis from other compound classes .…”

Antileishmanial and Cytotoxic Activity of Some Highly Oxidized Abietane Diterpenoids from the Bald Cypress, Taxodium distichum

“…The structures of all new isolated compounds were established by the interpretation of their spectroscopic and spectrometric properties, and the known compounds were identified by comparison of their experimental analytical data to published values. Thus, compounds 5 – 16 were identified as the known natural products microstegiol ( 5 ), taxoquinone ( 6 ), , royleanone ( 7 ), , horminone ( 8 ), 7 -O- methylhorminone ( 9 ), taxodione ( 10 ), , 12-hydroxy-6,7- seco -abieta-8,11,13-triene-6,7-dial ( 11 ), ferruginol ( 12 ), , sugiol ( 13 ), , 6α-hydroxysugiol ( 14 ), 6-hydroxy-5,6-dehydrosugiol ( 15 ), and 14-deoxycoleon U ( 16 ), while compound 3 has been described earlier only as a synthetic material, − and 4 was reported previously only as an intermediate product in the total synthesis of compound 5 …”

Asymmetric Diels−Alder Reactions of a New Enantiomerically Pure Sulfinylquinone: A Straightforward Access to Functionalized Wieland−Miescher Ketone Analogues with (R) Absolute Configuration

“…The use of sulfinyl benzoquinones as dienophiles for Diels−Alder reactions has experienced increased interest in recent years. , This methodology found its first synthetic application in the enantioselective synthesis of angucyclinones using an enantiomerically pure sulfinyl naphthaquinone as dienophile …”