Complementary chemistry! α-Isocupreine (-ICPN) was synthesized for the first time in one step from quinine by treatment with CF3SO3H (see scheme). This compound serves as an enantiocomplementary catalyst to β-isocupreidine (β-ICD) in the Morita–Baylis–Hillman reaction.
Stereochemical evidence is presented to demonstrate that (-)-inthomycin C has (3R)- and not (3S)-stereochemistry. Careful reappraisal of the previously published work2-5 now indicates that the Hatakeyama, Hale, Ryu, and Taylor teams all have synthesized (-)-(3R)-inthomycin C. The newly measured [α]D of pure (-)-(3R)-inthomycin C (98% ee) is -7.9 (c 0.33, CHCl3) and not -41.5 (c 0.1, CHCl3) as was previously reported in 2012.
A novel
formal [4 + 1]-cycloaddition of readily available homopropargyl
alcohols with diazo dicarbonyl compounds is described, which involves
tandem O–H insertion/Conia-ene cyclization under cooperative
Rh(II)/Zn(II) catalysis. This reaction provides easy access to various
substituted tetrahydrofurans and exhibits complete E-selectivity in the case of nonterminal alkynes.
The stereocontrolled total synthesis of (-)-cinatrin C1, a phospholipase A2 inhibitor, has been accomplished. The key feature includes the stereoselective construction of the highly substituted tetrahydrofuran core by In(OTf)3-catalyzed Conia-ene reaction of the oxygen-tethered acetylenic malonic ester followed by dihydroxylation with concomitant lactonization.
This novel ring closure reaction involves tandem OH insertion/Conia‐ene cyclization under cooperative Rh(II)/Zn(II) catalysis, providing access to substituted tetrahydrofurans with complete (E)‐selection in the case of nonterminal alkynes (XII).
The stereoselectivity is predominantly controlled by the catalyst and the conditions. In the amine-catalyzed reactions, the endo-isomer (III) is slightly dominant over the exo-isomer (IV). The products can be used for the efficient preparation of carbasugars. -(OKAMURA*, H.; URABE, F.; HAMADA, T.; IWAGAWA, T.; Bull. Chem. Soc. Jpn. 85 (2012) 5, 631-633, http://dx.doi.org/10.1246/bcsj.20110257 ; Grad. Sch. Sci. Eng., Kagoshima Univ., Kagoshima 890, Japan; Eng.) -M. Paetzel 37-129
A highly stereoselective base-catalyzed asymmetric Diels–Alder reaction of 3-hydroxy-2-pyrone and simple aryl vinyl sulfoxide is reported. Furthermore, the synthetic utility of the resulting product was demonstrated by the efficient asymmetric synthesis of β-l-carbafructopyranose and β-l-carbapsicopyranose.
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