Nicholas reactions with carboxylic acids for the synthesis of macrocyclic diolides

[reaction: see text] We have developed a new strategy for the preparation of diolides using a cascade of Nicholas reactions. The carboxylic acid nucleophiles in these reactions are virtually unstudied participants in transformations of this type. Using this methodology, a 16-membered cobalt-complexed cyclic diyne is available in 28% yield over eight steps (an average of 85% per step). We can also easily access the uncomplexed diolide in one additional step.     

Macrolides from the scent glands of the tropical butterflies Heliconius cydno and Heliconius pachinus

The four major components present in scent gland extracts of the male Costa Rica longwing butterflies Heliconius cydno and Heliconius pachinus were identified as 12- and 14-membered macrolides containing a C(18)-carbon skeleton. By use of micro-reactions and spectrometric examinations, structural proposals were made and subsequently proven by synthesis, using ring-closing-metathesis as the key steps. These macrolides, (9Z,11E,13S)-octadeca-9,11-dien-13-olide (5, S-coriolide), (9Z,11E,13S,15Z)-octadeca-9,11,15-trien-13-olide (6), (9Z,13S)-octadec-9-en-13-olide (13), and (9Z,11S)-octadec-9-en-11-olide (25), are biosynthetically obviously derived from oleic, linoleic, and linolenic acids. Their absolute configurations were determined by gas chromatographic investigations on chiral phases, showing all to possess (S)-configuration.     

Precision enzymatic polymerization to polyesters with lipase catalysts

Ring-opening polymerization of lactones with different ring-size has been achieved via lipase catalysis. Small-size (4-membered) and medium-size lactones (6- and 7-membered) as well as macrolides (12-, 13-, 16-, and 17-membered) were subjected to the lipase-catalyzed polymerization. The polymerization behaviors strongly depended on the lipase origin and the ring-size of the lactones. In using Pseudomonas family lipases as catalyst, the polymerization of macrolides showing much lower anionic polymerizability proceeded much faster than that of ϵ-caprolactone. The enzymatic polymerizability of the lactones was evaluated by Michaelis-Menten kinetics. V_max increased as a function of the ring-size, whereas K_m values were not so different with each other. The granular immobilized lipase derived from Candida antarctica. showed the extremely efficient catalysis in the polymerization of ϵ-caprolactone. Single-step synthesis of methacryl- and ω-alkenyl-type polyester macromonomers was achieved by the lipase-catalyzed polymerization of 13-membered lactone in the presence of vinyl esters acting as terminator. Lipase also catalyzed a polycondensation of dicarboxylic acid and glycol in the aqueous medium, in which the dehydration took place in water.     

Synthesis and Hydrogen Bonding Capabilities of Biphenyl-Based Amino Acids Designed To Nucleate beta-Sheet Structure

The syntheses of 3'-(aminoethyl)-2-biphenylpropionic acid (1) and 2-amino-3'-biphenylcarboxylic acid (2) are described. These residues were designed to nucleate beta-sheet structure in aqueous solution when incorporated into small, amphiphilic peptides in place of the backbone of the i + 1 and i + 2 residues of the beta-turn. N-Benzyl-3'-(2-(benzylamido)ethyl)-2-biphenylpropamide (3) and N-benzyl-(2-benzylamido)-3'-biphenylamide (4) were synthesized and studied as model compounds to investigate the hydrogen-bonding capabilities of residues 1 and 2, respectively. The X-ray crystal structure of 3 indicates that a 13-membered intramolecular hydrogen-bonded ring is formed, while the remaining amide proton and carbonyl are involved in intermolecular hydrogen bonding. Infrared and variable-temperature NMR experiments indicate that, in solution (CH(2)Cl(2)), 3 exists as an equilibrium mixture of the 13- and the 15-membered intramolecularly hydrogen-bonded conformers with the 15-membered ring conformer being favored. Amide 4 was shown to exist in solution (CH(2)Cl(2)) as an equilibrium mixture of the 11-membered intramolecular hydrogen-bonded ring and a nonbonded conformation. No contribution from the 9-membered hydrogen-bonded ring conformation was observed. The X-ray crystal structure of 4 indicated the absence of intramolecular hydrogen bonding in the solid state.     

Synthesis of novel 15-membered macrolide dimers

A series of novel dimers of 15-membered macrolides was synthesized and evaluated.The dimers exhibited excellent activity against erythromycin-susceptible S.pneumonia,but did not show any improved activity against erythromycin-resistant S. pneumoniae encoded by erm gene.     

Absolute stereochemistry of amphidinolides G and H

[structure: see text] Absolute stereochemistry of amphidinolides G (1) and H (2), potent cytotoxic 27- and 26-membered macrolides, respectively, isolated from a marine dinoflagellate Amphidinium sp., was determined by X-ray diffraction analysis, synthesis of a degradation product (3) of 2, and interconversion between 1 and 2.     

Highly chemo- and stereoselective intermolecular coupling of diazoacetates to give cis-olefins by using Grubbs second-generation catalyst

Highly stereoselective formation of cis-2-ene-1,4-diesters by homo- and heterocoupling of alpha-diazoacetates in the presence of Grubbs second-generation catalyst is demonstrated. The dual reactivity of the catalyst in alkene metathesis and diazocoupling has been exploited in the synthesis of 12-26-membered macrocyclic dienyl dilactones by one-pot carbene dimerisation/ring-closing metathesis.     

Synthesis of new 14-membered macrolide antibiotics via a novel ring contraction metathesis

[reaction: see text] A novel ring opening ring closing metathesis (ROM-RCM) was demonstrated for cyclic conjugated dienes, effecting the excision of a C(2)H(2) unit and a net ring contraction. Applying the ring contraction metathesis, new 14-membered ring macrolide antibiotics were synthesized in a single step from existing 16-membered ring macrolides. This new class of macrolide antibiotics will provide access to new therapeutics for the treatment of macrolide-resistant bacterial infections.     

Aigialomycins A-E, new resorcylic macrolides from the marine mangrove fungus Aigialus parvus

Aigialomycins A-E (2-6), new 14-membered resorcylic macrolides, were isolated together with a known hypothemycin (1) from the mangrove fungus, Aigialus parvus BCC 5311. Structures of these compounds, including absolute configuration, were elucidated by spectroscopic methods, chemical conversions, and X-ray crystallographic analysis. Hypothemycin and aigialomycin D (5) exhibited in vitro antimalarial activity with IC(50) values of 2.2 and 6.6 microg/mL, respectively, while other analogues were inactive. Cytotoxicities of these compounds were also evaluated.     

Eine neue Synthese von (±)-Pyrenophorin

A new Synthesis of (±)-Pyrenophorin The synthesis of pyrenophorin (I), a 16-membered dilactone metabolite of plant pathogenic fungi is described. Reaction of the Grignard reagent II with the activated succinic acid ester III gave the methyl (t-butyl)dimethylsilyloxy-oxo-octanoate IV which was converted into the corresponding ethylene acetal. Dehydrogenation via the benzeneselenenyl derivative lead to pyrenophorinic acid V with protected functional groups. Selective removal of silyl group followed by saponification of the ester group provided the ethylene acetal-hydroxy acid VI suitable for the cyclodimerisation reaction. This was effected with azodicarbonic acid ester and triphenylphosphine at ?40° in a dilute toluene solution. The 16-membered dilactones VII with protected carbonyl groups were isolated in 24% yield. Silver-ion induced cyclodimerisation of the S-2-pyridyl carbothioate of VI gave much lower yields. Removal of the acetal groups lead to (±)-pyrenophorin (I) and meso-pyrenophorin in about equal amounts.     

Galbonolides A and B - two new non-glycosidic antifungal macrolides from streptomyces galbus

The title compounds 1 and 2 have been isolated and their structures established; 1 and 2 represent new non-glycosidic 14-membered macrolides with significant antifungal activity.     

Rakanmakilactones A-F, new cytotoxic sulfur-containing norditerpene dilactones from leaves of Podocarpus macrophyllus var. maki

Six new S-containing norditerpene dilactones, rakanmakilactones A-F (5-10), were isolated from the leaves of Podocarpus macrophyllus D. Don var. maki Endl., along with four known norditerpene dilactones (1-4). Their structures, stereochemistry and absolute configurations were determined by spectroscopic studies (HRMS, IR, ¹H, ¹³C and 2D NMR), and single-crystal X-ray analyses. Rakanmakilactones were found to have a cytotoxic effect against P388 murine leukemia cells.     

Umamidierungsreaktionen an cyclischen Amino-amid-Systemen. 3. Mitteilung über Umamidierungsreaktionen

Transamidation Reactions with Cyclic Amino-amides Lactames which are substituted at the nitrogen atom by a 3-aminopropyl residue are transformed under base catalysis to cyclic amino-amides enlarged by 4 ring atoms. The formed ring must be at minimum 12-membered. Scheme 2 illustrates this result: the 8-membered 7 is transamidated in 96% yield to the 12-membered ring 8 (in the presence of potassium 3-aminopropylamid in 1, 3-propanediamine), the 9-membered 10 to the 13-membered ring 11 (97%) and the 11-membered 14 to the 15-membered ring 15 . Furthermore, the 13-membered ring 27 (Scheme 5) is transformed to the 17-membered 28 . In the case of the 15-membered lactame 15 it is demonstrated that 14 is not formed back under the conditions of the transamidation. Large ring lactames which are substituted at the nitrogen atom by a 3-(alkylamino) propyl group lead under base catalysis to an equilibrium mixture, e.g. the 17-membered 26 is in equilibrium with the 21-membered 29 . This result is similar to the behavior of the corresponding open-chain amino-amides [2]. Because of transannular interactions, the 11-membered ring 2 is not stable: transamidation of the 7-membered 1 (Scheme 1) doesn't give the expected 2 , but its water elimination product 3 in small yield. The N-tosyl derivative of 2 , namely 20 , is synthesized by an independent route (Scheme 3). Detosylation of 20 yields the 7-membered 1 instead of 2 . Concerning the mechanism of this interesting reaction see Scheme 4.     

Synthesis from L-menthol of optically active macrolides with <Emphasis Type="Italic">N</Emphasis>-containing (azine or hydrazide) groups

Potentially useful 15- and 20-membered macrolides containing azine or hydrazide groups were synthesized from L-menthol via [1+1]-condensation at room temperature of 3R,7-dimethyl-6-oxooctyl-3R,7-dimethyl-6-oxooctanoate, which was obtained from 3R,7-dimethyl-6-oxooctanal via a Tishchenko reaction, with hydrazine hydrate or malonic acid dihydrazide.     

Tricrilactones A–H,Potent Antiosteoporosis Macrolides with Distinctive Ring Skeletons from Trichocladium crispatum,an Alpine Moss-Associated Fungus

Tricrilactones A–H ( 1 – 8 ), a new family of oligomeric 10-membered macrolides featuring collectively five unique ring skeletons, were isolated from a hitherto unexplored fungus, Trichocladium crispatum. Compounds 1 and 7 contain two unconventional bridged (aza)tricyclic core skeletons, 2 , 3 , 5 , and 6 share an undescribed tetracyclic 9/5/6/6 ring system, 4 bears an uncommon 9/5/6/10/3-fused pentacyclic architecture, and 8 is a dimer bridged by an unexpected C−C linkage. Their structures, including absolute configurations, were elucidated by spectroscopic analysis, quantum chemical calculations, and X-ray diffraction analysis. Importantly, the absolute configuration of the highly flexible side chain of 1 was resolved by the asymmetric synthesis of its four stereoisomers. The intermediate-trapping and isotope labeling experiments facilitated the proposal of the biosynthetic pathway for these macrolides. In addition, their antiosteoporosis effects were evaluated in vivo (zebrafish).     

Stereoselective synthesis of the C3-C15 fragment of callyspongiolide

The synthesis of C3-C15 fragment of callyspongiolide, a 14-membered macrolides isolated from the marine sponge Callyspongia sp., which was collected from the Indonesia, is reported. Highlights of the synthesis include construction of E-olefin through Julia-Kocienski olefination, Brown asymmetric allylation and base-induced elimination reactions for propargyl alcohol synthesis.     

Synthesis and structure of novel cyclonucleoside analogues of uridine

Novel cyclonucleoside analogues of uridine having pentylene and hexylene linker between the 5′-O and 3-N positions (thereby generating a 13- and 14-membered ring, respectively) were synthesized from uridine via ring-closing metathesis. An example of cyclic dinucleosides having two butylene linkers between the 5′-O and 3-N positions (24-membered ring) was synthesized from uridine via tandem cross-metathesis and ring-closing metathesis.     

Motuporamines, anti-invasion and anti-angiogenic alkaloids from the marine sponge Xestospongia exigua (Kirkpatrick): isolation, structure elucidation, analogue synthesis, and conformational analysis.

Extracts of the sponge Xestospongia exigua collected in Papua New Guinea were positive in a new assay for anti-invasion activity. Bioassay-guided fractionation led to the identification of the three known motuporamines A (1), B (2), and C (3) along with the new motuporamines D (4), E (5), and F (6) and a mixture of G, H, and I (15). Motuporamines A (1), B (2), and C (3) and the mixture of G, H, and I (15) were responsible for the anti-invasion activity of the crude extract. Motuporamine C (3) has also been found to be anti-angiogenic. A series of analogues of the motuporamines have been synthesized and evaluated for anti-invasive activity. These SAR results revealed that a saturated 15-membered cyclic amine fused to the natural motuporamine diamine side chain (13) represented the optimal structure for anti-invasive activity in this family. Single-crystal X-ray diffraction analysis of one of the analogues 20 showed that in the solid state its 16-membered macrocyclic amine fragment adopted the [4444] quadrangular conformation predicted by calculations to be the lowest energy conformation for the corresponding cycloalkane, cyclohexadecane. These data along with literature X-ray data and conformational analysis for derivatives of azacyclotridecane have been used as precedents for predicting the lowest energy ring conformations of other motuporamines. The SAR data from the natural and synthetic motuporamines have been combined with the conformational analyses to provide an outline of the functionality and shape required for activity in this family of alkaloids and to design a new analogue 49 that showed good anti-invasion activity.     

Long-range intramolecular S → N acyl migration: a study of the formation of native peptide analogues via 13-, 15-, and 16-membered cyclic transition states

The intramolecular long-range S → N acyl migration via 13-, 15-, and 16-membered cyclic transition states to form native tetra- and pentapeptide analogues was studied on S-acylcysteine peptides containing β- or γ-amino acids. The pH-dependency study of the acyl migration via a 15-membered cyclic transition state indicated that the reaction is favored at a pH range from 7.0 to 7.6. Experimental observations are supported by structural and computational investigations.     

Zooxanthellamide Cs: vasoconstrictive polyhydroxylated macrolides with the largest lactone ring size from a marine dinoflagellate of Symbiodinium sp

Zooxanthellamide Cs (ZAD-Cs), C(128)H(220)N(2)O(53)S(2) (ca. 2.7 kDa), was obtained from a cultured marine dinoflagellate of the genus Symbiodinium as an inseparable isomeric mixture of polyhydroxylated 61- to 66-membered macrolides. The chemical structures of the components were clarified by detailed 2D NMR analysis to be the macrolactonized analogues of zooxanthellamide A (ZAD-A), which had been previously isolated from the same microalgae. Chemical lability of ZAD-Cs suggests that ZAD-A is an artifact derived from ZAD-Cs during the isolation steps. Three of the components possess the largest (63-, 64-, and 66-membered) ring sizes found to date among the natural macrolides. ZAD-Cs exhibited higher vasoconstrictive activity than that of the zooxanthellatoxins, the first vasoconstrictive macrolides from Symbiodinium sp. The structure-activity relationship suggests that the huge macrolactone structure is important for biological activity. The relationship between the structures of the polyol metabolites and the phylogenetic systematics of Symbiodinium sp. is also discussed.