Total synthesis of dysiherbaine

Total Synthesis of Neodysiherbaine A via 1,3-Dipolar Cycloaddition of a Chiral Nitrone Template

The total synthesis of neodysiherbaine A was achieved via 1,3-dipolar cycloaddition of a chiral nitrone template with a sugar-derived allyl alcohol in the presence of MgBr₂·OEt₂. This cycloaddition constructed the C2 and C4 asymmetric centers in a single step. Then reductive cleavage, intramolecular S_N2 reaction of the tertiary alcohol, and oxidation of the primary alcohol afforded neodysiherbaine A.

Total synthesis of (-)-dysiherbaine

The enantioselective synthesis of (-)-dysiherbaine (1) has been established with efficiency via a unique synthetic strategy involving the desymmetrization of 2-substituted glycerol to install a quaternary chiral carbon, which induces further stereochemistry in the bicyclic perhydrofuropyran through mercuriocyclization and epoxidation.

Stereocontrolled synthesis of substituted bicyclic ethers through oxy-Favorskii rearrangement: total synthesis of (±)-communiol E

The potential of the oxy-Favorskii rearrangement to form branched cis-fused bicyclic ethers was explored. Both tertiary and quaternary centers were constructed in highly stereospecific manners. Methanol and primary amines were effective nucleophiles for the rearrangement. The total synthesis of (±)-communiol E was achieved based on this method.

Synthesis of the dysiherbaine tetrahydropyran core utilizing improved tethered aminohydroxylation conditions

A concise stereoselective route to the dysiherbaine tetrahydropyran core was achieved in 9 steps and 39% overall yield. Donohoe's improved tethered aminohydroxylation conditions were employed to concurrently install the amino and alcohol groups and construct the tetrahydropyran ring, which features four contiguous cis-stereocenters.

Ligands for ionotropic glutamate receptors

Marine-derived small molecules and peptides have played a central role in elaborating pharmacological specificities and neuronal functions of mammalian ionotropic glutamate receptors (iGluRs), the primary mediators of excitatory synaptic transmission in the central nervous system (CNS). As well, the pathological sequelae elicited by one class of compounds (the kainoids) constitute a widely-used animal model for human mesial temporal lobe epilepsy (mTLE). New and existing molecules could prove useful as lead compounds for the development of therapeutics for neuropathologies that have aberrant glutamatergic signaling as a central component. In this chapter we discuss natural source origins and pharmacological activities of those marine compounds that target ionotropic glutamate receptors.

[2,3]-Sigmatropic rearrangements of 3-sulfinyl dihydropyrans: application to the syntheses of the cores of ent-dysiherbaine and deoxymalayamicin A

The [2,3]-sigmatropic rearrangement of a variety of configurationally stable diastereomeric allylic sulfinyl dihydropyrans, produced by base-promoted cyclization of sulfinyl dienols, has been studied. In some cases, the efficient transformation of these substrates into dihydropyranols required an in-depth study of reaction conditions, with the preferred protocol relying on the use of DABCO in warm toluene. This methodology has been applied to the syntheses of the cores of ent-dysiherbaine and deoxymalayamicin A by means of efficient tethered aminohydroxylations.

Effects of alpha-Alkoxy Substitution and Conformational Constraints on 6-exo Radical Cyclizations of Hydrazones via Reversible Thiyl and Stannyl Additions

Access to multifunctional hydrazones of relevance to dysiherbaine synthesis studies is described. Subsequent radical cyclizations of multifunctional hydrazones via a Si- and C-linked tethering strategy are shown to function effectively in 6-exo fashion. Conformational constraints are proposed to play a key role in suppressing unproductive premature reduction pathways. The stereochemical outcomes suggest that minimizing the dipole repulsion between neighboring C=N and C-O bonds favors a C(alpha)-C(=N) dihedral angle placing the C=N bond axial within a chairlike transition state, in contrast to the usual Beckwith-Houk model.

Synthesis of the dysiherbaine tetrahydropyran core employing a tethered aminohydroxylation reaction

A stereocontrolled and scalable synthesis of an advanced intermediate of the dysiherbaine tetrahydropyran core has been achieved in 11 steps and 27% overall yield. The key feature of this synthetic approach is the application of the Donohoe tethered aminohydroxylation reaction to install the amino diol and establish the four contiguous syn stereocenters on the tetrahydropyran ring.

Design, total synthesis, and biological evaluation of neodysiherbaine A derivative as potential probes

To enable studies to elucidate the detailed biological function of dysiherbaine and neodysiherbaine A, potent and subunit-selective agonists for ionotropic glutamate receptors, the derivative with a hydroxymethyl substituent at the C10 position has been developed. Preliminary biological evaluation of the analogue showed that a C10 hydroxymethyl substituent produced significant alterations in binding affinities for the ionotropic glutamate receptor subtypes.

A Highly Stereocontrolled Total Synthesis of (−)-Neodysiherbaine A

Neodysiherbaine A, a neuroexitotoxin occurring in a Micronesian marine sponge Dysidea herbacea, was synthesized from tri-O-acetyl-D-glucal with excellent stereocontrol. The method established enables us to obtain gram quantities of neodysiherbaine A and its related compounds.

Design, synthesis, and biological evaluation of a scaffold for iGluR ligands based on the structure of (−)-dysiherbaine

The design and synthesis of four 2,2-disubstituted dihydrobenzofurans that are structurally related to several glutamate-containing natural products, including (-)-dysiherbaine, is described. Biological evaluation of these analogs shows that one is a KA receptor antagonist and another is an NMDA receptor agonist.