Large scale preparation of versatile chiral auxiliaries derived from (S)‐proline<sup>1</sup>

Enders, Dieter; Kipphardt, Helmut; Gerdes, Peter; Breña-Valle, Leonardo J.; Bhushan, Vidya

doi:10.1002/bscb.19880970809

Cited by 116 publications

(23 citation statements)

References 40 publications

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“…Thus, enamine-mediated 1,4-addition of ( S )-citronellal ( 19a ) to methyl vinyl ketone (MVK) facilitated by the proline-derived catalyst 20 (5 mol%)8 and ethyl 3,4-dihydroxybenzoate ( 21 ) as a co-catalyst (20 mol%)9 furnished, after an intramolecular aldol condensation (KOH, n -Bu 4 NOH cat.) of the resulting ketoaldehyde product, 24( S ) enone 22a in 72% overall yield and 93% de.…”

Section: Resultsmentioning

confidence: 99%

Total Synthesis, Revised Structure, and Biological Evaluation of Biyouyanagin A and Analogues Thereof

et al. 2008

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Isolated from Hypericum species H. chinese L. var. salicifolium, biyouyanagin A was assigned structure 1a or 1b on the basis of NMR spectroscopic anaylsis. This novel natural product exhibited significant anti-HIV properties and inhibition of lipopolysaccharide-induced cytokine production. Described herein are the total syntheses of biyouyanagin A and several analogs (3-11), structural revision of biyouyanagin A to 2b, and the biological properties of all synthesized compounds. The total synthesis proceeded through cascade sequences that efficiently produced enantiomerically pure or enriched key building blocks 15b (ent-zingiberene) and 18 (hyperolactone C), and featured a novel [2+2] photoinduced cycloaddition reaction which occurred with complete regio-and stereoselectivity. Biological investigations with the synthesized biyouyangagins A (2-11) and hyperolactones C (12-16) revealed that the activity of biyouyanagin A most likely resides in its hyperolactone C structural domain.

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Section: Resultsmentioning

confidence: 99%

Total Synthesis, Revised Structure, and Biological Evaluation of Biyouyanagin A and Analogues Thereof

et al. 2008

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“…9 The diastereomeric ratios of epoxides 3-5 were about 91:9 (SM, pp. [13][14][15][16][17][18], somewhat lower than 95:5 dr reported for these compounds in the previous communication. 9 Hence, there was a need to compare the attractiveness of the newly synthesized and the original epoxybisabolenol pheromone samples.…”

Section: Resultsmentioning

confidence: 49%

Expedient synthesis of bisabolenol stink bug pheromones via stereodefined cyclohex-2-enones

Shirali

Guzman

Weber

et al. 2017

Tetrahedron Letters

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Expedient synthesis of bisabolenol stink bug pheromones via stereodefined cyclohex-2-enones, Tetrahedron Letters (2017), doi: http://dx. ABSTRACTWe recently synthesized all stereoisomers of 1,10-bisaboladien-3-ol and 10,11-epoxy-1-bisabolen-3-ol, including three stink bug pheromones, via a rhodium-catalyzed asymmetric addition of trimethylaluminum to diastereomeric mixtures of cyclohex-2-enones. However, yields of trans isomers were low, and scaling reactions using expensive catalysts were cumbersome. Now we describe a new synthesis of bisabolenol stink bug pheromones via (S)-and (R)-4-((R)-6-methylhept-5-en-2-yl)cyclohex-2-enones prepared by enantioselective Michael additions of methyl vinyl ketone to (S)-and (R)-citronellals and lithium hydroxide monohydratecatalyzed stereoselective cyclizations of intermediate ketoaldehydes. Addition of methyllithiumto these enones provided cis-and trans-1,10-bisaboladien-3-ols, which were separated by chromatography on silica and further converted to 10,11-epoxy-1-bisabolen-3-ols. Thus, we developed more convenient syntheses of pheromones of the rice stink bug, the harlequin bug, and brown marmorated stink bug.

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“…In the cases of the diamine 5 and (R)-2-methoxymethylpyrrolidine (RMP, 6), [14] the reaction occurred with good yields but poor stereoselectivities (Table 1, entries 5 and 6). Under the catalysis of (S)-2-(1-methoxy-1-ethylpropyl)-pyrrolidine (7), [15] no improved results with regard to both yield and stereoselectivity were obtained in comparison to catalyst 4 (Table 1, entry 7). Employing diarylprolinol silyl ether 8 [Ar = 3,5-(CF 3 ) 2 C 6 H 3 ] as catalyst, very low conversion of the starting material was observed after two hours ( Table 1, entry 8).…”

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confidence: 70%

Asymmetric Synthesis of 2,3,4‐Trisubstituted Functionalised Tetrahydrofurans via an Organocatalytic Michael Addition as Key Step

2010

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Abstract:The organocatalytic Michael addition of various aldehydes to (2E,4E)-ethyl 5-nitropenta-2,4-dienoate has been achieved under the catalysis of diphenylprolinol trimethylsilyl ether furnishing the products in good to excellent yields (61-94%) and high stereoselectivities (dr up to > 98:2, ee = 97 to > 99%). Starting from these Michael adducts, 2,3,4-trisubstituted functionalized tetrahydrofurans are available in two steps by reduction of the aldehyde followed by an intramolecular oxa-Michael addition in good yields (54-76%) and stereoselectivities (dr up to > 95:5, ee = 97 to > 99%).Keywords: asymmetric synthesis; Michael addition; nitroalkenes; organocatalysis; tetrahydrofurans After intensive investigations and tremendous progress in the last decade, organocatalysis has been developed to one of the main branches of asymmetric synthesis.[1] Within the field of organocatalysis, the amine-catalysed Michael addition of aldehydes and ketones to nitroalkenes via an enamine intermediate, which was independently discovered by List et al., Barbas et al. and our group, [2] has attracted great interest in recent years, since the resulting g-nitroaldehydes or ketones are precursors of many important compounds such as g-amino acids. Many efforts have been made to develop new efficient organocatalysts to expand the substrate spectrum of this Michael reaction or to involve it as a key step in domino reactions. [3][4][5] Our attention was drawn to (2E,4E)-ethyl 5-nitropenta-2,4-dienoate (B) as a Michael acceptor, because the 1,4-adducts (C) may be converted into 2,3,4-trisubstituted tetrahydrofurans (E) in two steps by reduction of the aldehyde followed by an intramolecular oxa-Michael addition (Scheme 1). Polysubstituted tetrahydrofurans are frequently found as sub-A C H T U N G T R E N N U N G units in many natural products such as Annonaceous acetogenins, [6] lignans, [7] polyether ionophores [8] and macrodiolides, [9] which possess various biological activities including antitumour, antihelmic, antimalarial, antimicrobial and antiprotozoal activity. Due to these important biological activities, many efforts have been made for the stereoselective synthesis of polysubstituted tetrahydrofurans. [10,11] Initially we performed the reaction with (2E,4E)-ethyl 5-nitropenta-2,4-dienoate (2) and 3 equivalents of propanal (1a) in dichloromethane at room temperature. The catalyst diphenylprolinol silyl ether 4 [12,13] (5 mol%) was used, which shows good catalytic activity and excellent asymmetric induction in enaminemediated Michael additions. Encouragingly, the reaction was complete within an hour affording the nitroaldehyde 3a in excellent yield (89%) and enantioselectivities (98% ee syn, 94% ee anti). However, only a moderate diastereoselectivity (syn:anti = 77:23) was achieved (Table 1, entry 1). A brief solvent screen was undertaken and it was found that excellent enantiomeric excesses were obtained in every solvent used Scheme 1. Asymmetric synthesis of 2,3,4-trisubstituted tetrahydrofurans -retrosynthetic analysis.

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Large scale preparation of versatile chiral auxiliaries derived from (S)‐proline¹

Cited by 116 publications

References 40 publications

Total Synthesis, Revised Structure, and Biological Evaluation of Biyouyanagin A and Analogues Thereof

Total Synthesis, Revised Structure, and Biological Evaluation of Biyouyanagin A and Analogues Thereof

Expedient synthesis of bisabolenol stink bug pheromones via stereodefined cyclohex-2-enones

Asymmetric Synthesis of 2,3,4‐Trisubstituted Functionalised Tetrahydrofurans via an Organocatalytic Michael Addition as Key Step

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Large scale preparation of versatile chiral auxiliaries derived from (S)‐proline1

Cited by 116 publications

References 40 publications

Total Synthesis, Revised Structure, and Biological Evaluation of Biyouyanagin A and Analogues Thereof

Total Synthesis, Revised Structure, and Biological Evaluation of Biyouyanagin A and Analogues Thereof

Expedient synthesis of bisabolenol stink bug pheromones via stereodefined cyclohex-2-enones

Asymmetric Synthesis of 2,3,4‐Trisubstituted Functionalised Tetrahydrofurans via an Organocatalytic Michael Addition as Key Step

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Large scale preparation of versatile chiral auxiliaries derived from (S)‐proline¹