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Stereoselective syntheses of 3-dehydroxynaltrexamines and N-methyl-3-dehydroxynaltrexamines.

ABSTRACT: Methodology is presented for the synthesis of 6α/β-3-dehydroxynaltrexamines and 6α/β- N-methyl-3-dehydroxynaltrexamines. A stereoselective route is provided for each target compound while a novel one-pot method for the synthesis of 6 α/β-3-N-methyl-3-dehydroxynaltrexamines is also explored. These results enable the versatile and efficient preparation of key epoxymorphinan intermediates to facilitate future selective opioid ligand discovery and development.

SUBMITTER: Li M

PROVIDER: S-EPMC7584067 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Stereoselective syntheses of 3-aminocyclooctanetriols and halocyclooctanetriols.

Project description:The efficient synthesis of two new stereoisomeric 3-aminocyclooctanetriols and their new halocyclitol derivatives starting from cis,cis-1,3-cyclooctadiene are reported. Reduction of cyclooctene endoperoxide, obtained by photooxygenation of cis,cis-1,3-cyclooctadiene, with zinc yielded a cyclooctene diol followed by acetylation of the hydroxy group, which gave dioldiacetate by OsO4/NMO oxidation. The cyclooctane dioldiacetate prepared was converted to the corresponding cyclic sulfate via the formation of a cyclic sulfite in the presence of catalytic RuO4. The reaction of this cyclic sulfate with a nucleophilic azide followed by the reduction of the azide group provided the target, 3-aminocyclooctanetriol. The second key compound, bromotriol, was prepared by epoxidation of the cyclooctenediol with m-chloroperbenzoic acid followed by hydrolysis with HBr(g) in methanol. Treatment of bromotriol with NaN3 and the reduction of the azide group yielded the other desired 3-aminocyclooctanetriol. Hydrolysis of the epoxides with HCl(g) in methanol gave stereospecifically new chlorocyclooctanetriols.

| S-EPMC7961859 | biostudies-literature

Stereoselective Syntheses of all the Possible Stereoisomers of Coronafacic Acid.

Project description:An efficient and stereoselective syntheses of all the possible stereoisomers of coronafacic acid (CFA) has been developed. The stereochemistries of C3a and C7a were controlled in a diastereoselective Diels-Alder type cycloaddition using a chiral auxiliary. CFA and 6-epi-CFA were synthesized by hydrogenation of a common intermediate. During the synthesis of 6-epi-CFA, we established that its cis-fused configuration is important for the introduction of C4-C5 double bond by dehydration. This report is the first practical synthesis of both 6-epi-CFA, and its enantiomer.

| S-EPMC7545439 | biostudies-literature

Stereoselective Syntheses of 3'-Hydroxyamino- and 3'-Methoxyamino-2',3'-Dideoxynucleosides.

Project description:Aminonucleosides are used as key motifs in medicinal and bioconjugate chemistry; however, existing strategies toward 3'-hypernucleophilic amine systems do not readily deliver deoxyribo-configured products. We report diastereoselective syntheses of deoxyribo- and deoxyxylo-configured 3'-hydroxyamino- and 3'-methoxyamino-nucelosides from 3'-imine intermediates. The presence or absence of the 5'-hydroxyl-group protection dictates facial selectivity via inter- or intramolecular delivery of hydride from BH3 (borane). Protecting group screening gave one access to previously unknown 3'-methoxyamino-deoxyguanosine derivatives.

| S-EPMC7007280 | biostudies-literature

Concise and Stereoselective Total Syntheses of Annotinolides C, D, and E.

Project description:The annotinolides are one of the most recent additions to the Lycopodium family of alkaloids, with its members possessing challenging, caged structures that include a [3.2.1]-bicyclic core bearing six contiguous stereocenters, including four that are fully substituted. Herein, we document a concise and stereoselective route that achieves the first total syntheses of three of its members: annotinolides C, D, and E. Key operations include a gold(I)-catalyzed Conia-ene reaction that fashions much of the main core in a single operation, as well as a number of other challenging and chemoselective transformations to generate the remaining elements. Moreover, efforts utilizing the natural products themselves, seeking adjustments in their oxidation states and the rearrangement of individual ring systems, shed light on their potential biogenesis with some outcomes counter to those originally proposed. Finally, formal enantioenriched syntheses of the target molecules are also presented.

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Ruthenium- and palladium-catalyzed enyne cycloisomerizations: differentially stereoselective syntheses of bicyclic structures.

Project description:Enyne cycloisomerizations can provide an efficient means for forming carbon-carbon bonds. We describe stereoselectively dichotomous enyne cycloisomerizations, entirely dependent on the selection of catalytic manifold. Ruthenium catalysis provides trans-fused bicyclic systems, whereas palladium catalysis provides the analogous cis-fused bicycles. A number of substrates are investigated, and the outcomes ultimately offer a clear mechanistic rationale for these observations.

| S-EPMC2665024 | biostudies-literature

Total syntheses of amphidinolides T1 and T4 via catalytic, stereoselective, reductive macrocyclizations.

Project description:Described in this work are total syntheses of amphidinolides T1 and T4 using two nickel-catalyzed reductive coupling reactions of alkynes, with an epoxide in one case (intermolecular) and with an aldehyde in another (intramolecular). The latter was used to effect a macrocyclization, form a C-C bond, and install a stereogenic center with >10:1 selectivity in both natural product syntheses. Alternative approaches in which intermolecular alkyne-aldehyde reductive coupling reactions would serve to join key fragments were investigated and are also discussed; it was found that macrocyclization (i.e. intramolecular alkyne-aldehyde coupling) was superior in several respects (diastereoselectivity, yield, and length of syntheses). Alkyne-epoxide reductive couplings were instrumental in the construction of key fragments corresponding to approximately half of the molecule of both natural products. In one case (T4 series), the alkyne-epoxide coupling exhibited very high site selectivity in a coupling of a diyne. A model for the stereoselectivity observed in the macrocyclizations is also proposed.

| S-EPMC3148192 | biostudies-literature

Stereoselective syntheses of the C(1)-C(9) fragment of amphidinolide C.

Project description:Stereoselective syntheses of the C(1)-C(9) fragments 18 and 28 of amphidinolide C have been developed. The first-generation sequence involves a diastereoselective chelate-controlled [3 + 2]-annulation reaction of 6 and 7, while the second-generation synthesis involves an intramolecular hetero-Michael cyclization of 8.

| S-EPMC2650083 | biostudies-literature

Quantitative Prediction of Rate Constants for Aqueous Racemization To Avoid Pointless Stereoselective Syntheses.

Project description:Racemization has a large impact upon the biological properties of molecules but the chemical scope of compounds with known rate constants for racemization in aqueous conditions was hitherto limited. To address this remarkable blind spot, we have measured the kinetics for racemization of 28 compounds using circular dichroism and 1 H?NMR spectroscopy. We show that rate constants for racemization (measured by ourselves and others) correlate well with deprotonation energies from quantum mechanical (QM) and group contribution calculations. Such calculations thus provide predictions of the second-order rate constants for general-base-catalyzed racemization that are usefully accurate. When applied to recent publications describing the stereoselective synthesis of compounds of purported biological value, the calculations reveal that racemization would be sufficiently fast to render these expensive syntheses pointless.

| S-EPMC5820753 | biostudies-literature

Stereoselective Syntheses and Application of Chiral Bi- and Tridentate Ligands Derived from (+)-Sabinol.

Project description:A library of bidentate diols, as well as tridentate triols and aminodiols, derived from (+)-sabinol, was synthesized in a stereoselective manner. Sabinol was transformed into allylic trichloroacetamide via Overman rearrangement of the corresponding trichloroacetimidate. After changing the protecting group to Boc, the enamine was subjected to stereospecific dihydroxylation with OsO?/NMO, resulting in the (1R,2R,3R,5R)-aminodiol diastereomer. The obtained primary aminodiol was transformed to a secondary analogue. The ring closure of the N-benzyl-substituted aminodiol with formaldehyde was investigated and regioselective formation of the spiro-oxazolidine ring was observed. Hydroboration or dihydroxylation of sabinol or its benzyl ether with OsO?/NMO resulted in the formation of sabinane-based diols and triols following a highly stereospecific reaction. Treatment of sabinol with m-CPBA afforded O-benzoyl triol as a diastereoisomer of the directly dihydroxylated product, instead of the expected epoxy alcohol. The resulting aminodiols, diol, and triols were applied as chiral catalysts in the reaction of diethylzinc and benzaldehyde from moderate to good selectivity.

| S-EPMC6017647 | biostudies-literature

Stereoselective Total Syntheses of Acutifolone A, Bisacutifolone A and B, Pinguisenol, and Isonaviculol.

Project description:Stereoselective total syntheses of pinguisane type of sesquiterpenoids are described following a unified approach using a chiral building block derived from (R)-pulegone. The functionality embodied in the key intermediate enables their facile elaboration into more complex structures of biological relevance such as acutifolone A (9 steps, 22% overall yield) and bisacutifolone A and B (6 and 8%, respectively) following Furukawa's modified Simmons-Smith cyclopropanation, Luche reduction, Saegusa-Ito oxidation, pyridinium chlorochromate-mediated 1,3-oxidative transposition, and Diels-Alder dimerization as key steps.

| S-EPMC6641225 | biostudies-literature

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