Abstract We report herein an efficient synthesis of fully Boc‐protected, up to 13‐meric polymer 1,3‐propanediamine. The was facilitated by one‐pot conversion (up six) N ‐Ns groups ‐Boc under conditions 1) PhSH and Cs 2 CO 3 for deprotection the Ns group, followed 2) Boc O protection. average yield per group extremely high, especially substrates with four six (94.6%–96.6%).

A synthesis of the C14-C35 segment macrolide ring model poecillastrin C has been achieved. The C14-C23 was synthesized by stereoselective Mukaiyama aldol reaction between ketene silyl N,O-acetal possessing chiral oxazolidinone auxiliary and O-acetyl lactol prepared conjugate addition followed iodolactonization. C24-C35 constructed three vinylogous reactions. Both segments were coupled diisobutylaluminium hydride (DIBALH) reduction to produce moiety macrocyclic model.

Abstract A convergent, iterative, and split-couple strategy for synthesis of homogeneous polymer 1,3-propanediamine (long-chain polyamine, LCPA) has been developed, by employing 1,3-dibromopropane as a glue in subunit couplings. By this synthetic strategy, 7-, 11-, 15-mer LCPAs were successfully synthesized. This solved problems that had arisen with previous methods, such variable reactivity poor reproducibility.

Absolute configuration at 12 stereocenters in the 36-membered macrocyclic ring portion of poecillastrin C (

Poecillastrin H (1), a chondropsin-type macrolide with conjugated pentaene moiety, was isolated from the Characella sp. marine sponge. The planar structure of 1 elucidated by analysis spectroscopic data. absolute configuration β-hydroxyaspartic acid residue (β-OHAsp) determined to be d-threo Marfey's analysis, and mode lactone ring formation through OHAsp chemical degradation. extremely sensitive toward light showed potent cytotoxic activity against 3Y1 cells an IC50 value 4.1 nM.

The isolation and structural determination of new marine ladder-frame polyethers, brevisulcatic acids-1 (1) -4 (2) are reported. Brevisulcatic acids were isolated from the dinoflagellate Karenia brevisulcata, which was identified as causative species a major red tide event in New Zealand 1998. ether ring composition β-hydroxy, γ-methylene valeric acid side chain 1 2 common, but has γ-lactone 5-membered A-ring while is seco analogue. Compound bioactivity similarities to brevetoxin A.

The planar structure of poecillastrin C (1) was revised through selective reduction the ester carbon. absolute configuration β-hydroxyaspartic acid (OHAsp) residue determined to be d-threo by Marfey's analysis. hydrolysate product 1 liberated (2R,3R)-2-amino-3,4-dihydroxybutanoic acid, demonstrating that β-carboxyl group in esterified. structures poecillastrins B-D and 73-deoxychondropsin A were also revised.

By establishing the procedures for sequential deprotections, reaction monitoring, purification, and handling, first time, we achieved total synthesis of proposed structure protoaculeine B (2), which is a highly hydrophilic polycationic amino acid. The NMR mass spectra chemical reactivity synthetic sample differed from those natural B, indicates necessity revision originally reported structure.

The structure of protoaculeine B, the N-terminal residue marine peptide toxin aculeine is revised to cis-1,3-disubstituted tetrahydro-β-carboline framework. We prepared two truncated model compounds that lack a long-chain polyamine using one-step Pictet–Spengler reaction tryptophan and compared their NMR, mass spectra, chemical reactivity with those natural B. synthetic models reproduced profiles product well, which confirmed appropriateness revision.

Abstract Here, we report an empirical model for diastereoselective cyclopropanation of fumarate/maleate diesters with chloroacetate, sulfonium ylide, or ammonium ylide. With symmetrical diesters, was found to proceed a high level diastereoselectivity in favor the chiral isomer. In contrast, production meso isomer observed 38–48% when unsymmetrical employed. An improved synthesis (N-desmethy)dysibetaine CPa both racemic and enantiomerically pure forms furthermore achieved. Configurational...

Direct comparison of authentic ciliatamide A with four synthetic isomers (1–4) by means NMR and chiral-phase HPLC revealed that possesses the 12R (d-N-MePhe residue) 22S (l-Lys configurations, which were not identical either our previous assignment or those proposed others through total synthesis. The absolute configuration methionine sulfoxide residue in D was also revised to be d.

Abstract Here, we report a practical method for asymmetric synthesis of cyclopropane-fused GABA analogs. Starting from 2-furaldehyde, the cis-isomer (CAMP) was synthesized over 10 steps; (−)- and (+)-CAMP·HCl were by employing d- l-menthol as chiral auxiliary total 2.5% 1.3% yields, respectively. On other hand, trans-isomer (TAMP) elaborated via double induction, i.e. organocatalytic cyclopropanation on substrate. Thus, starting l- d-menthyl acrylate, in combination with quinidine-derived...

Two different types of polycyclic ether toxins, namely brevisulcenals (KBTs) and brevisulcatic acids (BSXs), produced by the red tide dinoflagellate Karenia brevisulcata, were cause a toxic incident that occurred in New Zealand 1998. Four major components, KBT-F, -G, -H, -I, shown to be cytotoxic lethal mice, isolated from cultured K. brevisulcata cells, their structures elucidated spectroscopic analyses. analogues, brevisulcenal-A1 (KBT-A1) brevisulcenal-A2 (KBT-A2), toxins higher polarity...

Polyamines are ubiquitously found in nature. In this paper, we disclose our iterative coupling strategy for the synthesis of a structurally defined polymer 1,3-propanediamine, and can be used both initially proposed structure revised protoaculeine B isolated from marine sponge. We first attempted polyamines using "the Ns strategy" but that polyamine with eleven groups has solubility problems. then examined versatility photoremovable NPEC protecting group synthesis. Finally, suitably...

Abstract Herein, we report our results on the synthetic studies of originally proposed structure protoaculeine B, isolated from a marine sponge. Starting tryptophan, two candidates suitably protected heterotricyclic subunits were stereoselectively synthesized over 8 and 16 steps, respectively. Furthermore, diastereomeric amino acids, finally synthesized, found to be neuroactive: (9 S *,11 *)‐isomer with natural‐type configuration was hyperactive, whereas R hypoactive upon mice...

Herein, we report the enantiospecific synthesis of two artificial glutamate analogs designed based on IKM-159, an antagonist selective to AMPA-type ionotropic receptor. The features chiral resolution carboxylic acid intermediate by esterification with ʟ-menthol, followed a configurational analysis NMR, conformational calculation, and X-ray crystallography. A mice in vivo assay showed that (2 R )-MC-27, six-membered oxacycle, is neuroactive, whereas S )-counterpart inactive. It was also found...

By a hybrid design of naturally derived excitatory amino acids, dysiherbaines and kainic acid, we have successfully developed series artificial glutamate analogs with sp3-rich scaffold via domino Ugi/Diels-Alder reaction, metathesis reaction oxanorbornenes as key steps. All the first-generation were found to be neuronally active upon mice intracerebroventricular injection. As second-generation analogs, then synthetically modified heterotricyclic structure, that carbonyl group on A-ring still...

Herein we report stereoselective formation of 1,3-dioxanes by oxa-Michael reaction cis-arranged δ-siloxyenones using 1,3,5-trioxane and methanesulfonic acid (MsOH). The yields were satisfactory ranging from 81% to 95% (five examples). We furthermore studied the ester analog with same combination reagents found that tetrahydropyran Prins takes place in moderate yield 68%. This methodology would be generally employed synthesis heterocyclic systems which are otherwise not readily accessible....