Asymmetric synthesis of a key synthetic precursor for(+)-strigol and sorgolactone

Schröer, Josef; Welzel, Peter

doi:10.1016/s0040-4020(01)81337-5

Cited by 16 publications

(6 citation statements)

References 49 publications

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“…The absolute configuration of 2b was determined based on the known ( R )‐stereoselectivity of OYE3 in the reduction of substrate 2a 16. The absolute configurations of 4b and 5b were determined by performing the bioreduction of 4a and 5a with baker’s yeast with known stereochemistry 17,23. Similarly, the absolute configurations of 6a and 6b were determined via kinetic resolution catalyzed by lipases according to a published protocol 24.…”

Section: Resultsmentioning

confidence: 99%

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Enzymatic Synthesis of Optically Active Lactones via Asymmetric Bioreduction using Ene‐Reductases from the Old Yellow Enzyme Family

2015

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In contrast to the widely studied asymmetric bioreduction of α,β‐unsaturated carboxylic acid esters catalyzed by ene‐reductases, the reaction applied to lactones remains unexplored. A broad set of ene‐reductases was found to reduce various α‐, β‐ and γ‐substituted α,β‐unsaturated butyrolactones to yield the corresponding saturated non‐racemic lactones. Substitution patterns greatly influenced activities and stereoselectivities and lactone products were obtained in moderate to excellent yields; importantly, enzyme‐based stereocontrol allowed access to both enantiomers in up to >99% ee. Chiral recognition of a distant γ‐center led to kinetic resolution with remarkable enantioselectivities (E values up to 49). An unprecedented case of dynamic kinetic resolution was observed with 3‐methyl‐5‐phenylfuran‐2(5H)‐one, whereby spontaneous racemization of the substrate furnished the product in up to 73% conversion and >99% ee and 96% de.

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Section: Resultsmentioning

confidence: 99%

“…After 72 h reaction time, ( R )‐ 4b was obtained; yield: 13.0 mg (0.07 mmol, 35%). Comparison of the optical rotation ([α]${{{20\hfill \atop {\rm D}\hfill}}}$ : +13, c =0.69, CHCl 3 ) with the literature value ([α]${{{20\hfill \atop {\rm D}\hfill}}}$ : +43, c =6.40, CHCl 3 ) assigned the absolute configuration as ( R )‐ 4b 23…”

Section: Methodsmentioning

confidence: 99%

Enzymatic Synthesis of Optically Active Lactones via Asymmetric Bioreduction using Ene‐Reductases from the Old Yellow Enzyme Family

2015

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“…However, by using excess NaBH 4 and 18 mol % of NiCl 2 in methanol, [11] the sole product isolated was the undesired diastereomer 12.…”

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confidence: 99%

“…The planned 1,4-reduction of the lactone C À C double bond in the presence of the decalin C À C double bond of 4 was expected to proceed chemo-and diastereoselectively from the face opposite the two pseudoaxial methyl groups to afford 11. However, by using excess NaBH 4 and 18 mol % of NiCl 2 in methanol, [11] the sole product isolated was the undesired diastereomer 12. [12] It can be seen from molecular modeling studies that the bicyclic subunit represented by the middle ring and the lactone is bent, thus allowing ready nucleophilic attack from the convex face of 4.…”

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confidence: 99%

Stereoselective Synthesis of Superambrox: Stereoselective Type III Intramolecular Ene Reaction and OH‐Assisted Ru‐Catalyzed Isomerization

Fehr

Farris

2006

Angew Chem Int Ed

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Dedicated to Professor Georg Frµter on the occasion of his 65th birthdayIn the 1990s, chemists from Firmenich [1a] reported the isolation of (À)-1 by chemical degradation of the labdane diterpene (+)-larixol.[1b] This unsaturated analogue of Ambrox [2] was named "Superambrox" as a result of its excellent odor qualities (Scheme 1).To our knowledge, the only synthetic approaches towards Superambrox are based on acid-mediated polyene cyclizations, [3] which afford the racemate with low stereoselectivity in only moderate yields. We now report a concise, highly selective synthesis of racemic Superambrox (AE )-1. The creation of the CÀC double bond in a highly substituted environment presents a special challenge, as this subunit is known to be prone to isomerization or skeletal rearrangement. A second difficulty lies in the stereoselective elaboration of the heterocycle.Our synthetic plan consists of the development of a new tandem type III intramolecular ene reaction/Oppenauer oxidation of dihydro-b-C14-aldehyde (2), a high-tonnage raw material, thus allowing a direct approach to the decalone 3, which has the properly positioned double bond. Acetoxylation from the less-hindered a face followed by intra-

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“…Two attempted syntheses of 2a have been reported. [16] [17] We recently reported the synthesis and biological evaluation of (±)-2aϪ(±)-2d [18] and the synthesis of (ϩ)-2a from (S)-(Ϫ)-citronellal [19] as preliminary communications, while Zwanenburg and co-workers synthesized (ϩ)-2a and ent-(Ϫ)-2b together with the Scheme 1. Structures of strigol and sorgolactone four racemates.…”

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confidence: 99%

Syntheses of (±)- and (+)-Sorgolactone, the Germination Stimulant fromSorghum bicolor

et al. 1999

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Syntheses of (±)‐2a, the racemate of the structure proposed for sorgolactone, and its three racemic stereoisomers have been accomplished with confirmation of the stereostructures of the intermediate (±)‐10 and the final product (±)‐2a by X‐ray analysis. Its optically active form, (3aR,8S,8bS,2′R)‐(+)‐2a, has also been prepared from (S)‐(–)‐citronellal by employing radical cyclization of 18 to 19 as the key step. Spectroscopic properties of the synthetic products are compared with those reported for natural sorgolactone. Bioassays using clover broomrape (Orobanche minor) seeds have revealed that all the stereoisomers strongly stimulate their germination.

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Asymmetric synthesis of a key synthetic precursor for(+)-strigol and sorgolactone

Cited by 16 publications

References 49 publications

Enzymatic Synthesis of Optically Active Lactones via Asymmetric Bioreduction using Ene‐Reductases from the Old Yellow Enzyme Family

Enzymatic Synthesis of Optically Active Lactones via Asymmetric Bioreduction using Ene‐Reductases from the Old Yellow Enzyme Family

Stereoselective Synthesis of Superambrox: Stereoselective Type III Intramolecular Ene Reaction and OH‐Assisted Ru‐Catalyzed Isomerization

Syntheses of (±)- and (+)-Sorgolactone, the Germination Stimulant fromSorghum bicolor

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