Total Syntheses of (−)‐Conduritol B ((−)‐1L‐Cyclohex‐5‐ene‐1,3/2,4‐tetrol) and of (+)‐Conduritol F((+)‐1D‐Cyclohex‐5‐ene‐1,2,4/3‐tetrol). Determination of the Absolute Configuration of (+)‐Leucanthemito

Abstract

The 'naked sugar' (+)-(1R,2R,4R)-2-endo-cyano-7-oxabicyclo[2.2.l]hept-5-en-2-exo-yl acetate ((+)-4) was converted (7 steps, 45 % overall) with high stereoselectivity into (-)-(4R,5S,6R)-4,5,6-tris{[(tert-butyl)dimethylsilyl]oxy}cyclohex-2-en-l-one ((-)-11). Reduction of (-)-11 with NaBH4.CeC1,.7 H,O, followed by deprotection of the silyl ether moieties gave (+)-conduritol F ((+)-1; 47 %) whose characteristics were identical to those of natural (+)-leucanthemitol. Reduction of (-)-I1 with DIBAH, followed by deprotection of the silyl ether moiety led to (-)-conduritol B ((-)-3; 51 %).

5a-Carba-β-D-, 5a-Carba-β-L- and 5-Thio-β-L-xylopyranosides as New Orally Active Venous Antithrombotic Agents

“…The reduction of (AE)-11 under Luches conditions [13] provided a 2.5 : 1 mixture of conduritol derivatives (AE)-12 and (AE)-13 in 84% yield. Compound (AE)-10 was obtained in 8 steps and 50% yield following Le Drians method [11]. Applying Allemanns modification [14], (AE)-10 was derived from (AE)-7 in 4 steps and 37% overall yield ( Scheme 1).…”

“…± Since the ethereal link between the conduritol-B moiety and the aglycone (4-ethyl-7-hydroxy-2H-1-benzopyran-2-one) will be generated through a S N 2 displacement, a suitably semi-protected conduritol-F intermediate was required. Among the numerous synthesis of conduritol-F that have been proposed [10], the one by Le Drian [11] has demonstrated that racemic (AE)-12 can be derived from the Diels-Alder adduct (AE)-7 of furan to 1-cyanovinyl acetate via (AE)-8 ± 11, whereas enantiomerically pure ()-12 and (À)-12 can be derived with the same ease from the Diels-Alder adducts of furan to enantiomerically pure 1-cyanovinyl esters [12]. The synthesis of (AE)-12 [11] involves the base-induced isomerization of the 7-oxabicyclo[2.2.1]heptan-2-one derivative (AE)-10 into cyclohex-2-enone (AE)-11 (91%).…”

“…Among the numerous synthesis of conduritol-F that have been proposed [10], the one by Le Drian [11] has demonstrated that racemic (AE)-12 can be derived from the Diels-Alder adduct (AE)-7 of furan to 1-cyanovinyl acetate via (AE)-8 ± 11, whereas enantiomerically pure ()-12 and (À)-12 can be derived with the same ease from the Diels-Alder adducts of furan to enantiomerically pure 1-cyanovinyl esters [12]. The synthesis of (AE)-12 [11] involves the base-induced isomerization of the 7-oxabicyclo[2.2.1]heptan-2-one derivative (AE)-10 into cyclohex-2-enone (AE)-11 (91%). The reduction of (AE)-11 under Luches conditions [13] provided a 2.5 : 1 mixture of conduritol derivatives (AE)-12 and (AE)-13 in 84% yield.…”

“…Enantiomerically pure (À)-10 was prepared according to the Le Drians method [11]. Alternatively, it was obtained by the Johnson-Zeller [15] resolution of (AE)-10: The products of addition of the lithium conjugate base of ()-( S )-N,S-dimethyl-S-phenylsulfoximide to (AE)-10 were separated by flash chromatography (silica gel) yielding ()-14 (42%) and (À)-15 (39%).…”

Studies Towards the Synthesis of Salvinorin A

“…Ether cleavage of 12a and 12b using tert-butyldimethylsilyl(trifluoromethane)sulfonate (TBDMSOTf) in the presence of base as reported by Vogel et al [29] gave unexpected results. The appearance of furan signals in 13 C NMR and a propionate ester in 1 H NMR analysis indicated C-C bond cleavage had occurred between the ester and the tertiary bridgehead (C1, C2) to give 14.…”