SciCombinator

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Concept: Paclitaxel total synthesis

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A synthesis fit for a king: The total synthesis of (±)-kingianins A, D, and F has been achieved in ten steps. Key features include the gram-scale synthesis and partial reduction of a conjugated tetrayne to a (Z,Z,Z,Z)-tetraene, the domino 8π-6π electrocyclic ring closure of a (Z,Z,Z,Z)-tetraene, and the radical-cation-catalyzed formal Diels-Alder dimerization of functionalized bicyclo[4.2.0]octadiene precursors.

Concepts: Total synthesis, Paclitaxel total synthesis, Chemical synthesis, Vector space, Formal language

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The total synthesis of the Lycopodium alkaloid lyconadin A was accomplished and it was applied to the total syntheses of the related congeners, lyconadins B, and C. Lyconadin A has attracted attention as a challenging target for total synthesis due to the unprecedented pentacyclic skeleton. Our synthesis of lyconadin A features a facile construction of the highly fused tetracyclic skeleton through a combination of an aza-Prins reaction and an electrocyclic ring opening followed by a formation of a C-N bond. Transformation of the bromoalkene moiety of the tetracycle to a key enone intermediate was extensively investigated, and three methods via sulfide, oxime, or azide intermediates were established. A pyridone ring was constructed from the key enone interme-diate to complete the synthesis of lyconadin A. A dihydropyridone ring could also be formed from the same enone intermediate, leading to a synthesis of lyconadin B. Establishment of the conditions for an electrocyclic ring opening without formation of the C-N bond resulted in completion of the total synthesis of lyconadin C.

Concepts: Chemical reaction, Functional group, Total synthesis, Paclitaxel total synthesis, Chemical synthesis, Rational number, Functional groups, Reserpine

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An efficient total synthesis of (-)-epothilone B has been achieved in ca. 8% yield over 11 steps from 9 (or 10 steps from 7/8), which features a bissiloxane-tethered ring closing metathesis reaction to approach the trisubstituted (Z) double bond and forms a new basis for further development of an industrial process for epothilone B and ixabepilone.

Concepts: Total synthesis, Paclitaxel total synthesis, Olefin metathesis, Chemical synthesis, Epothilone, Process management, Ixabepilone, Sorangium cellulosum

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2-Methoxymethylpyrrolidine best performed, among several other proline derivatives, to control the enantioselective [3+3] annulation of beta-(hetero)aryl-alpha nitro-alpha,beta-enals with commercial 2,2-dimethyl-1,3-dioxan-5-one, a procedure which renders highly-oxygenated nitrocyclohexanes endowed with five new stereocenters. Use of this reaction allowed the development of a total synthesis of the antitumoral natural product (+) pancratistatin; it also converted our previous racemic route to tetrodotoxin into an enantioselective one.

Concepts: Chemical reaction, Total synthesis, Paclitaxel total synthesis, English-language films, Chemical synthesis, Enantiomer, Paclitaxel, Racemic mixture

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A very simple and efficient stereoselective approach to cis-2,3-disubstituted piperdines via the reduction of N-acyl iminium ion intermediates is described. Application of this methodology is exemplified by the enantioselective total synthesis of (+)-(2S, 3S)-CP-99,994.

Concepts: Total synthesis, Paclitaxel total synthesis, Chemical synthesis, Ammonium, Iminium

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Palladium-catalyzed cyclization of imines has been developed to construct the extremely rare 3H-pyrrolo[2,3-c]quinoline ring system for diversity oriented first total synthesis of antimalarial marine natural product Aplidiopsamine A as well as synthesis of Marinoquinoline A and potential natural product hybrid NCLite-M1.

Concepts: Total synthesis, Paclitaxel total synthesis, Integer, Imine, Natural product, Paclitaxel, Multiplication, Natural products

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The concise total syntheses of the bis(pyrroloindolines) (-)-lansai B and (+)- nocardioazines A and B are reported. The key pyrroloindoline building blocks are rapidly prepared by enantioselective formal [3+2] cycloaddition reactions. The macrocycle of (+)-nocardioazine A is constructed by an unusual intramolecular diketopiperazine formation.

Concepts: Chemical reaction, Total synthesis, Paclitaxel total synthesis, Chemical synthesis, The Key, Cycloaddition

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We report the enantiospecific total synthesis of (+)-tubingensin A. Our synthesis features an aryne cyclization to efficiently introduce the vicinal quaternary stereocenters of the natural product and proceeds in only 9 steps (longest linear sequence) from known compounds.

Concepts: Total synthesis, Paclitaxel total synthesis, Natural number, Isomorphism, Integer, Partially ordered set, Ordinal number, Well-order

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Progress toward the total synthesis of bielschowskysin is described including introduction of the quaternary C12 and neighboring C13 stereocenters.

Concepts: Total synthesis, Paclitaxel total synthesis, Chemical synthesis

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The first enantioselective total syntheses of virosaine A and bubbialidine are described. Key transformations include the formation of a tetracyclic intermediate via an intramolecular aza-Michael addition, generation of a N-hydroxy-pyrrolidine through a Cope elimination and an intramolecular [1,3]-dipolar cycloaddition to generate a complex 7-oxa-1-azabicyclo[3.2.1]octane ring system.

Concepts: Total synthesis, Paclitaxel total synthesis, Chemical synthesis, Vector space, Alkene, Real number, Integer, Elimination reaction