Isolation and Structure Determination of a New Sesquiterpene Lactone fromNauplius aquaticus

Abstract

The aerial part of Nauplius aquaticus afforded a new sesquiterpene lactone with a humulanolide skeleton, 6,7,9,10-tetrahydroasteriscunolide (1), in addition to the known asteriscunolides A (2) and D (3). Their structures were established principally by two-dimensional NMR spectroscopy.

Ruthenium-Catalyzed Metathesis Cascade Reactions in Natural Products Synthesis

“…The 1 H and 13 C NMR spectra of 6,7,9,10-tetrahydroasteriscunolide were almost identical to those of the natural product except for the chemical shifts of two carbon atoms. [39] Despite this small difference, the optical rotation of the synthetic material ([a]26D = À 6.3 (c = 0.40, CHCl 3 ) was in agreement with that of the natural product ([a]20D = À 17.5 (c = 1.0, CHCl 3 )). The structure of the newly synthesized 6,7,9,10-tetrahydroasteriscunolide was subsequently confirmed by X-ray crystallography, which therefore suggested that the original 13 C NMR spectrum of the material should be revised.…”

“…( − )‐Asteriscunolide D underwent a regio‐ and stereoselective hydrogenation reaction in the presence of Wilkinson's catalyst to afford 6,7,9,10‐tetrahydroasteriscunolide exclusively in 99 % yield. The 1 H and 13 C NMR spectra of 6,7,9,10‐tetrahydroasteriscunolide were almost identical to those of the natural product except for the chemical shifts of two carbon atoms . Despite this small difference, the optical rotation of the synthetic material ([α]26D=−6.3 ( c= 0.40, CHCl 3 ) was in agreement with that of the natural product ([α]20D=−17.5 ( c= 1.0, CHCl 3 )).…”

“…[37] From a structural perspective, most of the compounds belonging to this structural class possess unique and synthetically challenging molecular architectures. Asteriscunolides A-D and 6,7,9,10tetrahydroasteriscunolide contain a synthetically challenging 11-membered ring, [38,39,40] together with a bridged cyclic Scheme 2. Total syntheses of (-)-norsecurinine and (+)-allonorsecurinine using a relay ring closing metathesis cascade reaction.…”

“…From a structural perspective, most of the compounds belonging to this structural class possess unique and synthetically challenging molecular architectures. Asteriscunolides A–D and 6,7,9,10‐tetrahydroasteriscunolide contain a synthetically challenging 11‐membered ring, together with a bridged cyclic butenolide moiety (Figure ). Asteriscanolide, 6,7,9,10‐tetradehydroasteriscanolide, naupliolide and aquatolide have a rather unusual bicyclo[6.3.0]undecane core, as well as an adjoining butyrolactone moiety .…”

Collective Synthesis of Natural Products by Using Metathesis ­Cascade Reactions

“…33 From a structural perspective, most of the compounds in this structural class have unique and challenging structures. Asteriscunolides A-D 34 and 6,7,9,10-tetrahydroasteriscunolide 35 contain a synthetically challenging eleven-membered ring, 36 together with a bridged cyclic butenolide moiety (Figure 2). Asteriscanolide, 37 6,7,9,10-tetradehydroasteriscanolide, 38 naupliolide, 39 and aquatolide 40 have a rather unusual bicyclo[6.3.0]undecane core, as well as an adjoining butyrolactone moiety.…”