Batzelladine Alkaloids Research Articles

Short‐Cut Bio‐Inspired Synthesis of Tricyclic Guanidinic Motifs of Crambescidins and Batzelladines Marine Alkaloids

We report a convenient short synthesis of tricyclic guanidine‐containing natural products model featuring four‐component reaction between 2,5‐dimethoxytetrahydrofuran, 2‐aminopyrimidine and two acylacetic or benzoylacetic acids. A synthetic route combining the Robinson–Schöepf bioinspired strategy and biomechanistic analysis of the crambescidin and batzelladine alkaloids family. An application of this strategy to the synthesis of two unnatural stereoisomers of merobatzelladine B is described from the protected guanidine in the form of aminopyrimidine.

Desymmetrization of meso-2,5-diallylpyrrolidinyl ureas through asymmetric palladium-catalyzed carboamination: stereocontrolled synthesis of bicyclic ureas.

Desymmetrization of meso-2,5-diallylpyrrolidinyl ureas through asymmetric palladium-catalyzed carboamination: stereocontrolled synthesis of bicyclic ureas.

Asymmetric Total Synthesis of (+)‐Merobatzelladine B

Asymmetric Total Synthesis of (+)‐Merobatzelladine B

Synthesis of 7-epineoptilocaulin, mirabilin B, and isoptilocaulin. A unified biosynthetic proposal for the ptilocaulin and batzelladine alkaloids. Synthesis and structure revision of netamines E and G.

Addition of guanidine to a 6-methylhexahydroindenone in MeOH at 85 degrees C afforded 7-epineoptilocaulin. A similar reaction with a 6-propylhexahydroindenone afforded netamine E. MnO2 oxidation of 7-epineoptilocaulin and netamine E afforded mirabilin B and netamine G, respectively. The netamines have the side chains trans, not cis as was initially proposed. A unified biosynthetic scheme for the batzelladines and ptilocaulin family is proposed. Conjugate addition of guanidine to a bis enone followed by an intramolecular Michael reaction of the enolate to the other enone, aldol reaction, dehydration, and enamine formation will lead to a tricyclic intermediate at the dehydroptilocaulin oxidation state. 1,4-Hydride addition will lead to ptilocaulin or 7-epineoptilocaulin depending on which face the hydride adds to. 1,2-Hydride addition will lead to isoptilocaulin. The key tricyclic intermediate was prepared from a tetrahydroindenone and guanidine and reduced with NaBH4 to give a mixture rich in ptilocaulin and isoptilocaulin.

Batzelladine alkaloids from the caribbean sponge Monanchora unguifera and the significant activities against HIV-1 and AIDS opportunistic infectious pathogens

Five new polycyclic guanidine alkaloids, 16β-hydroxycrambescidin 359 ( 1), batzelladines K, L, M, and N ( 2– 5), along with the previously reported ptilomycalin A ( 6), crambescidine 800 ( 7), batzelladine C ( 8), and dehydrobatzelladine C ( 9), were isolated from the Jamaican sponge Monanchora unguifera. Their structures were assigned on the basis of detailed analysis of 1D and 2D NMR, and mass spectral data. Their activities against cancer cell lines, protozoa, HIV-1 and AIDS opportunistic infectious pathogens (AIDS-OIs) including Mtb were evaluated.

Total synthesis of (+)-batzelladine A and (-)-batzelladine D via [4 + 2]-annulation of vinyl carbodiimides with N-alkyl imines.

A diastereoselective [4 + 2]-annulation of vinyl carbodiimides with chiral N-alkyl imines has been developed to access the stereochemically rich polycyclic guanidine cores of the batzelladine alkaloids. Application of this strategy, together with additional key steps such as long-range directed hydrogenation and diastereoselective intramolecular iodo-amination, led to highly convergent total syntheses of (-)-batzelladine D and (+)-batzelladine A with excellent stereocontrol.

Concise Synthesis of Guanidine-Containing Heterocycles Using the Biginelli Reaction

Two general methods for the synthesis of 2-imino-5-carboxy-3,4-dihydropyrimidines were developed using the three-component Biginelli reaction. The first method utilizes pyrazole carboxamidine, a beta-ketoester, and an aldehyde in an initial Biginelli reaction. After Boc protection, these products undergo aminolysis and acidic deprotection to generate 2-imino-5-carboxy-3,4-dihydropyrimidines in a four-step sequence. The second method utilizes a triazone-protected guanidine, a beta-ketoester, and an aldehyde in a Biginelli reaction. Acidic cleavage of the triazone yields 2-imino-5-carboxy-3,4-dihydropyrimidines in a two-step sequence. We also describe the further elaboration of several of these products using a tethered Biginelli reaction to give triazaacenaphthalene structures similar to those found in crambescidin and batzelladine alkaloids.

Evolution of a Strategy for the Synthesis of Structurally Complex Batzelladine Alkaloids. Enantioselective Total Synthesis of the Proposed Structure of Batzelladine F and Structural Revision.

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Evolution of a Strategy for the Synthesis of Structurally Complex Batzelladine Alkaloids. Enantioselective Total Synthesis of the Proposed Structure of Batzelladine F and Structural Revision

Stereoselective synthesis of octahydro-5,6,6a-triazaacenaphthalenes 29 and 34 having the anti-relationship of the angular hydrogens flanking the pyrrolidine nitrogen confirmed suspicions that the relative configuration of the left-hand tricyclic guanidine fragment of batzelladine F should be revised to have the syn relationship of these hydrogens. Several strategies were examined for coupling tricyclic guanidine fragments to prepare potential structures for batzelladine F. Eventually, a convergent synthesis strategy was devised, whose central step was a fragment-coupling tethered-Biginelli reaction (Scheme 17). Using this approach we synthesized four potential structures of batzelladine F, 35-38. None of these compounds, nor their enantiomers, were identical to natural batzelladine F. Reinvestigation of mass spectra of natural batzelladine F, and fragments 88 and 89 obtained upon saponification of batzelladine F, demonstrated that the originally proposed connectivity of this alkaloid was also incorrect. The revised connectivity, 90, of natural batzelladine F depicted in Scheme 21 is proposed.

Diastereoselective [4 + 2] Annulation of Vinyl Carbodiimides with N‐Alkyl Imines. Asymmetric Synthetic Access to the Batzelladine Alkaloids.

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Diastereoselective [4+2] Annulation of Vinyl Carbodiimides with N-Alkyl Imines. Asymmetric Synthetic Access to the Batzelladine Alkaloids

A diastereoselective [4+2] annulation of vinyl carbodiimides with chiral N-alkyl imines has been developed to access the stereochemically rich tricyclic core of the batzelladine alkaloids. Its application to the asymmetric synthesis of batzelladine D permitted the use of long-range, directed hydrogenation and stereoselective intramolecular iodoamination as additional key steps to establish the remaining stereocenters within the natural product with excellent stereocontrol.

Studies Towards the Total Synthesis of Batzelladine A.

Application of a diastereoselective three-component coupling to the bicyclic core of the batzelladine alkaloids is described. The synthesis features the elaboration of glutamic acid by use of Eschenmoser sulfide contraction. An earlier approach is also included, which shows some limitations of dithiane chemistry when applied to the particular compounds required for this target.

Studies towards the total synthesis of batzelladine A.

Application of a diastereoselective three-component coupling to the bicyclic core of the batzelladine alkaloids is described. The synthesis features the elaboration of glutamic acid by use of Eschenmoser sulfide contraction. An earlier approach is also included, which shows some limitations of dithiane chemistry when applied to the particular compounds required for this target.

Assembling polycyclic bisguanidine motifs resembling batzelladine alkaloids by double tethered Biginelli condensations.

[reaction: see text] Double tethered Biginelli condensations furnish linked polycyclic bisguanidines or bisureas. Alteration of the bis-beta-ketoester component allows bispolycyclic guanidine motifs to be constructed that resemble natural batzelladine alkaloids or have novel linkages.

Total Synthesis of Batzelladine D.

[structure: see text] Stereoselective total synthesis of batzelladine D was accomplished in 15 steps. This synthesis features (i) successive 1,3-dipolar cycloaddition reactions to form the 2,5-disubstituted pyrrolidine ring system, (ii) esterification of the side chain to the bicyclic guanidine carboxylate, a common synthetic intermediate of batzelladine alkaloids, and (iii) tricyclic guanidine formation under the Mitsunobu reaction conditions.

Studies towards the total synthesis of Batzelladine A: synthesis of a model pyrrolo[1,2- c]pyrimidine

A new approach to the synthesis of fragments related to the batzelladine alkaloids has been developed using a formal asymmetric aza-Diels–Alder reaction.

Stereoselective synthesis of tricyclic guanidine, the key component of the batzelladine alkaloids

Stereoselective and efficient synthesis of tricyclic guanidine, the key component of batzelladines A and D, was accomplished based on successive 1,3-dipolar cycloadditions and successive cyclizations for the construction of the tricyclic guanidine ring.

Total synthesis of batzelladine D.

[structure: see text] Stereoselective total synthesis of batzelladine D was accomplished in 15 steps. This synthesis features (i) successive 1,3-dipolar cycloaddition reactions to form the 2,5-disubstituted pyrrolidine ring system, (ii) esterification of the side chain to the bicyclic guanidine carboxylate, a common synthetic intermediate of batzelladine alkaloids, and (iii) tricyclic guanidine formation under the Mitsunobu reaction conditions.

ChemInform Abstract: Application of the Tethered Biginelli Reaction for Enantioselective Synthesis of Batzelladine Alkaloids. Absolute Configuration of the Tricyclic Guanidine Portion of Batzelladine B.

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Application of the Tethered Biginelli Reaction for Enantioselective Synthesis of Batzelladine Alkaloids. Absolute Configuration of the Tricyclic Guanidine Portion of Batzelladine B.

Tethered Biginelli condensation of enantioenriched hexahydropyrrolopyrimidines 8 with beta-ketoesters provides efficient asymmetric access to tricyclic guanidines 9 having a syn relationship of the angular C2a and C8a hydrogens. This reaction was employed to realize the first practical enantioselective access to this fragment of batzelladine alkaloids B (2) and E (5). The efficiency of this strategy is illustrated in the synthesis of the dextrorotatory enantiomer of batzelladine B methanolysis product 10 in 10 steps and 25% overall yield from 2-nonanone and methyl acetoacetate. The asymmetric synthesis of 10 establishes that the absolute configuration of the tricyclic portion of batzelladine B (2) is 25aR,28S,30R. The 4-methyl-7-alkyl-1,2,2a,3,4,5,6,7,8,8a-decahydro-5,6,8b-triazaacenaphthalene-3-carboxylic acid subunit, e.g., 29, of batzelladine alkaloids A (1), D (4), F (6), and G was also prepared for the first time by catalytic hydrogenation of tricyclic guanidines 26 having the 2a,8a-anti stereochemistry.