Asymmetric Diels-Alder reactions: EPC-synthesis of a stable sarkomycin precursor (cyclosarkomycin)

Linz, G.; Weetman, J.; Hady, A. F. Abdel; Helmchen, Günter

doi:10.1016/s0040-4039(01)93809-2

Cited by 41 publications

(11 citation statements)

References 23 publications

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“…35 Further transformation of 19a with LiAlH 4 was conducted to afford 20 in 94% yield, which is a key intermediate of (+)-sarkomycin. 36 Other C-, N-, O-, P-, and S-nucleophiles could also be used, and the corresponding novel 1,4-adducts 19b−g were selectively obtained via exo-facial addition (Figure 5c). The transformations to optically active functionalized norbornenes 19a−g are valuable, since they have not been synthesized directly in DA reactions using less reactive electron-rich β-substituted acroleins or acrylates.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…On the other hand, the addition of benzyl alcohol under conventional basic conditions gave 1,4-adduct 19a in 93% yield with high diastereoselectivity (dr = 98:2) . Further transformation of 19a with LiAlH 4 was conducted to afford 20 in 94% yield, which is a key intermediate of (+)-sarkomycin . Other C-, N-, O-, P-, and S-nucleophiles could also be used, and the corresponding novel 1,4-adducts 19b – g were selectively obtained via exo -facial addition (Figure c).…”

Section: Resultsmentioning

confidence: 99%

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Chiral Supramolecular U-Shaped Catalysts Induce the Multiselective Diels–Alder Reaction of Propargyl Aldehyde

et al. 2018

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The Diels–Alder reaction, which is a traditional [4 + 2] cycloaddition with two carbon–carbon bond formations, is one of the most powerful tools to synthesize versatile and unique six-membered rings. We show that chiral supramolecular U-shaped boron Lewis acid catalysts promote the unprecedented multiselective Diels–Alder reaction of propargyl aldehyde with cyclic dienes. Independent from the substrate control, enantio-, endo/exo-, π-facial-, regio-, site-, and substrate-selectivities could be controlled by the present U-shaped catalysts. The obtained reaction products could access the concise synthesis of chiral diene ligands and a key intermediate of (+)-sarkomycin. The results presented here might partially contribute to the development of artificial enzyme-like supramolecular catalysts for multiselective reactions, which will be able to target organic compounds that have thus far eluded synthesis.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Chiral Supramolecular U-Shaped Catalysts Induce the Multiselective Diels–Alder Reaction of Propargyl Aldehyde

et al. 2018

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“…These compounds were chosen as substrates taking into account that some of the expected addition products are precursors of natural carbocyclic compounds with important biological activity. Particularly interesting are cyclopentenone derivatives, as the resulting adducts possess substructures present in a large number of natural products of interest [117] including jasmonoids, and prostaglandins, and cyclopentenoid antibiotics, such as methylenomycin A, [118] methylenomycin B, xanthocydin, [119] cyclosarkomycin, [120] and sarkomycin. [121] Additionally, compounds 221-227 have the practical advantage of a stable C=C configuration, which simplifies their synthesis and avoid considering eventual E/Z isomerization (Scheme 39).…”

Section: Addition To Activated Cyclic Alkenesmentioning

confidence: 99%

Aldehyde N,N‐Dialkylhydrazones as Neutral Acyl Anion Equivalents: Umpolung of the Imine Reactivity

et al. 2007

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The isoelectronic replacement of the α‐carbon of enamines by nitrogen leads to the corresponding hydrazones, and thus, they can be termed “aza‐enamines”. Hence, aldehyde N,N‐dialkylhydrazones enable analogous electrophilic substitutions at the imine carbon that corresponds to the β‐carbon of enamines. In addition, after hydrolysis of the product hydrazones to the parent ketones or aldehydes, these reactions constitute an umpolung of the classical carbonyl reactivity and overall a nucleophilic acylation or formylation. This review covers the aza‐enamine chemistry from its very beginning in the late 1960s up to this year. In the first part, reactions of aromatic, aliphatic, and heterocyclic aldehyde N,N‐dialkylhydrazones with highly reactive substrates such as the Vilsmeier and Mannich reagents, sulfonyl isocyanates, perfluoroacetic anhydride, and inorganic electrophiles such as halogens and phosphorus tribromide are described. The hydrazones of α,β‐unsaturated aldehydes react as vinylogous aza‐enamines at the terminal carbon providing unsaturated aldehydes. As electron‐rich dienes and dienophiles, they also form Diels–Alder adducts and thus interesting N‐heterocycles. The second part covers carbon–carbon bond formations of the sterically less‐demanding formaldehyde N,N‐dialkylhydrazones with synthetically very useful electrophiles such as various Michael acceptors and carbonyl compounds. Formaldehyde SAMP‐hydrazone and related derivatives generally give excellent asymmetric inductions. Finally, first organocatalytic versions of the aza‐enamine chemistry are presented. In summary, the rich chemistry of aldehyde N,N‐dialkylhydrazones as neutral acyl anion, formyl anion, and cyanide equivalents is demonstrated. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

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“…Some of the syntheses addressed the racemic mixture and involve a relatively large number of steps . In other cases, the desired enantiopurity was obtained via (a) kinetic resolution, (b) the chiral auxiliary approach, or (c) classical racemic resolution . However, most of these processes gave low overall yields.…”

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confidence: 99%

Total Synthesis of (R)-Sarkomycin Methyl Ester via Regioselective Intermolecular Pauson–Khand Reaction and Iridium-Catalyzed Asymmetric Isomerization

et al. 2018

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A new five-step enantioselective synthesis of ( R)-sarkomycin methyl ester is described. The cyclopentane scaffold was built by a regioselective intermolecular Pauson-Khand reaction. Enantioselectivity was introduced by a novel Ir-catalyzed isomerization reaction. The last steps involved a catalytic hydrogenation of the exocylic double bond, followed by the deprotection and elimination of the amino group. This route is the shortest enantioselective synthesis of this antibiotic reported to date.

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Asymmetric Diels-Alder reactions: EPC-synthesis of a stable sarkomycin precursor (cyclosarkomycin)

Cited by 41 publications

References 23 publications

Chiral Supramolecular U-Shaped Catalysts Induce the Multiselective Diels–Alder Reaction of Propargyl Aldehyde

Chiral Supramolecular U-Shaped Catalysts Induce the Multiselective Diels–Alder Reaction of Propargyl Aldehyde

Aldehyde N,N‐Dialkylhydrazones as Neutral Acyl Anion Equivalents: Umpolung of the Imine Reactivity

Total Synthesis of (R)-Sarkomycin Methyl Ester via Regioselective Intermolecular Pauson–Khand Reaction and Iridium-Catalyzed Asymmetric Isomerization

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