Octane Moiety Research Articles

Scaffold hopping in the oxadiazole antibiotic structure leads to more active compounds

Isosteric replacement of the oxadiazole ring by amide bond in the structure of new non-β-lactam antibiotics led to compounds with higher activity against Gram-positive pathogens of ESKAPE panel. A series of 17 compounds were synthesized by acylation of 4-(4-fluorophenoxy)aniline with various amino acids. The spirocyclic derivative with 6-methylsulfonyl-2,6-diazaspiro[3.4]octane moiety showed excellent minimum inhibitory concentrations of 0.093–0.75 μg ml−1 against a number of methicillin-resistant Staphylococcus aureus strains.

Enantioselective total synthesis of (‒)-lucidumone enabled by tandem prins cyclization/cycloetherification sequence

The Ganoderma meroterpenoids are a growing class of natural products with architectural complexity, and exhibit a wide range of biological activities. Here, we report an enantioselective total synthesis of the Ganoderma meroterpenoid (‒)-lucidumone. The synthetic route features several key transformations, including a) a Cu-catalyzed enantioselective silicon-tethered intramolecular Diels-Alder cycloaddition to construct the highly functionalized bicyclo[2.2.2]octane moiety; b) Brønsted acid promoted tandem O-deprotection/Prins cyclization/Cycloetherification sequence followed by oxidation to install concurrently the tetrahydrofuran and the fused indanone framework; c) Fleming-Tamao oxidation to generate the secondary hydroxyl; d) an iron-catalyzed Wacker-type oxidation of hindered vinyl group to methyl ketone.

Pleosmaranes A-R, Isopimarane and 20-nor Isopimarane Diterpenoids with Anti-inflammatory Activities from the Mangrove Endophytic Fungus Pleosporales sp. HNQQJ-1.

Pleosmaranes A-R (1-18), 18 new isopimarane-type diterpenoids, together with four known analogs (19-22), were isolated from the mangrove endophytic fungus Pleosporales sp. HNQQJ-1. Their structures and absolute configurations were established by analysis of their spectroscopic data and electronic circular dichroism (ECD) calculations. Compounds 1-9 possess an unusual aromatic B ring and a 20-nor-isopimarane skeleton. Compounds 15-17 contain a unique 2-oxabicyclo[2.2.2]octane moiety. Compound 18 features an unexpected 2-oxabicyclo[3.2.1]octane moiety. Compounds 8 and 12 exhibited a moderate inhibitory effect against LPS-induced NO production, with IC50 values of 19 and 25 μM, respectively.

Highly methoxylated neolignans from the endangered plant Yulania cylindrica and their chemotaxonomic significance

Three previously undescribed highly methoxylated neolignans, cylindrienones A‒C (1–3, resp.), together with five related known neolignans (4–8) were isolated from the twigs and leaves of the ornamental and medicinal plant Yulania cylindrica, a ‘vulnerable’ species endemic to China. The new structures were established by spectroscopic methods including HRESIMS, 2D-NMR, and electronic circular dichroism (ECD). The known ones were identified by comparing their observed and reported physicochemical properties and spectroscopic data. Compounds 1 and 2 are (C8–C3')-neolignan derivatives possessing a unique cyclohexadienone unit, while compound 3 is a rearranged neolignan containing a rare tricycle [4.2.0.02,8]octane moiety. Compounds 1–8 were isolated from Y. cylindrica for the first time. Compounds 4 and 7 were even firstly found from the family Magnoliaceae. The chemotaxonomic significance of the isolated methoxylated neolignans was briefly discussed.

Horsfielenigans A and B, Two Rearranged Lignans with Anti-inflammatory Effects from Horsfieldia kingii.

Seven lignans were isolated from 70% aqueous acetone extracts of the twigs and leaves of Horsfieldiakingii. Among these, new compounds 1-3 were identified by spectroscopic techniques, with horsfielenigans A and B (1 and 2) being particularly noteworthy for their rare β-benzylnaphthalene skeleton, where compound 1 contains an oxabicyclo[3,2,1]octane moiety. In vitro evaluation of bioactivity against nitric oxide (NO) production in LPS-activated RAW264.7 macrophages revealed inhibitory effects by 1 (IC50 = 7.3 μM) and 2 (IC50 = 9.7 μM).

A pair of new enantiomeric hybrid phthalide–adenines with a rare 5-oxa-1-azaspiro[3,4]octane moiety and two pairs of new enantiomeric hybrid paraethyl phenol–adenines from Ligusticum chuanxiong

Three pairs of new enantiomeric adenine alkaloids, (+)/(−)-liguadenines A–C [(+)/(−)-1–3], were isolated from the rhizome of Ligusticum chuanxiong Hort. The structures and absolute configurations of these compounds were determined using spectroscopic data, single-crystal X-ray diffraction, and electronic circular dichroism analyses. To the best of our knowledge, compounds (+)-1 and (−)-1 are the first hybrid phthalide–adenines to be ever reported. The linkage between the phthalide and adenine units in these compounds forms a rare 5-oxa-1-azaspiro[3,4]octane moiety. Analyses of the anti-inflammatory activities of the isolated compounds show that (+)/(−)-1 and (+)-3 exhibit significant inhibitory activity against LPS-induced TNF-α and IL-6 production in RAW264.7 cells. RT-qPCR analysis confirms that the most active compound, (+)-3, exerts anti-inflammatory activity by downregulating the mRNA expressions of TNF-α and IL-6 in the cells.

Alscholarines A and B, two rearranged monoterpene indole alkaloids from Alstonia scholaris.

Alscholarines A and B (1 and 2), two unprecedented rearranged monoterpene indole alkaloids, were isolated from Alstonia scholaris. Alscholarine A (1) features an imidazole ring fused with a rearranged vallesamine-type alkaloid possessing an unparalleled 6/5/6/6 tetracyclic skeleton through an unprecedented C7-C-19 connectivity. Alscholarine B (2), incorporating an unusual 7-oxa-1-azabicyclo[3.2.1]octane moiety, represents a unique rearranged vallesamine-type alkaloid with a 6/5/6/6/5 ring system via an unprecedented C-6-C-20 connectivity. Their structures were established by spectroscopic analysis, X-ray crystallography, and quantum-chemical calculations. Their plausible biosynthetic pathways were proposed. The vasorelaxant and anti-inflammatory activities of them were also evaluated. Compounds 1-3 showed moderate vasorelaxant activities.

Total Synthesis of Mollanol A.

Mollanol A is the first isolated member of the mollane-type grayanoids which possesses an unprecedented C-nor-D-homograyanane carbon skeleton and an 5,8-epoxide. Due to its transcriptional activation effects on the Xbp1 upstream promoters in different cell types, it has a potential therapeutic effect on inflammatory bowel disease. Here we report the first total synthesis of mollanol A, which constitutes a 15-step synthesis from commercially available materials via a convergent strategy. The synthesis involves an InCl3-catalyzed Conia-ene cyclization reaction to construct the bicyclo[3.2.1]octane moiety and a vinylogous aldol reaction/intramolecular oxa-Michael addition sequence to rapidly assemble the oxa-bicyclo[3.2.1] core.

Divergent Total Syntheses of Napelline-Type C20-Diterpenoid Alkaloids: (-)-Napelline, (+)-Dehydronapelline, (-)-Songorine, (-)-Songoramine, (-)-Acoapetaldine D, and (-)-Liangshanone.

The napelline-type alkaloids possess an azabicyclo[3.2.1]octane moiety and an ent-kaurane-type tetracyclic skeleton (6/6/6/5) along with varied oxidation patterns embedded in the compact hexacyclic framework. Herein, we disclose a divergent entry to napelline-type alkaloids that hinges on convergent assembly of the ent-kaurane core using a diastereoselective intermolecular Cu-mediated conjugate addition and subsequent intramolecular Michael addition reaction as well as rapid construction of the azabicyclo[3.2.1]octane motif via an intramolecular Mannich cyclization. The power of this strategy has been demonstrated through efficient asymmetric total syntheses of eight napelline-type alkaloids, including (-)-napelline, (-)-12-epi-napelline, (+)-dehydronapelline, (+)-12-epi-dehydronapelline, (-)-songorine, (-)-songoramine, (-)-acoapetaldine D, and (-)-liangshanone.

Ab Initio Study of Octane Moiety Adsorption on H- and Cl-Functionalized Silicon Nanowires.

Using first-principles calculations based on density functional theory, we investigated the effects of surface functionalization on the energetic and electronic properties of hydrogenated and chlorinated silicon nanowires oriented along the <112> direction. We show that the band structure is strongly influenced by the diameter of the nanowire, while substantial variations in the formation energy are observed by changing the passivation species. We modeled an octane moiety absorption on the (111) and (110) surface of the silicon nanowire to address the effects on the electronic structure of the chlorinated and hydrogenated systems. We found that the moiety does not substantially affect the electronic properties of the investigated systems. Indeed, the states localized on the molecules are embedded into the valence and conduction bands, with no generation of intragap energy levels and moderated change in the band gap. Therefore, Si-C bonds can enhance protection of the hydrogenated and chlorinated nanowire surfaces against oxidation without substantial modification of the electronic properties. However, we calculated a significant charge transfer from the silicon nanowires to the octane moiety.

Octacyclic and decacyclic ent‑abietane dimers with cytotoxic activity from Euphorbia fischeriana steud.

A novel Diels-Alder adduct possesses a 6/6/6/5/6/6/6/6 octacyclic skeleton featured with bicyclo[2.2.2]octane moiety, biseupyiheoid A (1), along with another decacyclic 6/6/6/3/5/6/5/6/6/6 fused diterpenoid dimer, bisfischoid C (2), were isolated from Euphorbia fischeriana. Their structures were determined by spectroscopic, X-ray crystallographic approaches, and quantum mechanical calculations. The structural features of 1 and 2 were hypothesized to involve intramolecular Diels-Alder reactions with different coupling patterns. Dimer 1 showed antiproliferative activity through apoptosis activation in LoVo cells.

Divergent Total Synthesis of Four Kopsane Alkaloids: N‐Carbomethoxy‐10,22‐dioxokopsane, Epikopsanol‐10‐lactam, 10,22‐Dioxokopsane, and N‐Methylkopsanone

AbstractWe have achieved the divergent total synthesis of four kopsane alkaloids which share a complex heptacyclic caged ring system. Key transformations include an asymmetric Diels–Alder reaction to assemble the central bicyclo[2.2.2]octane moiety and the quaternary stereocenter at C20, a SmI2‐mediated cascade reduction/aldol reaction to construct the five‐membered ring and the quaternary stereocenter at C7, and a late‐stage cascade reductive amination/cyclization to establish the highly strained caged ring system.

Divergent Total Synthesis of Four Kopsane Alkaloids: N-Carbomethoxy-10,22-dioxokopsane, Epikopsanol-10-lactam, 10,22-Dioxokopsane, and N-Methylkopsanone.

We have achieved the divergent total synthesis of four kopsane alkaloids which share a complex heptacyclic caged ring system. Key transformations include an asymmetric Diels-Alder reaction to assemble the central bicyclo[2.2.2]octane moiety and the quaternary stereocenter at C20, a SmI2 -mediated cascade reduction/aldol reaction to construct the five-membered ring and the quaternary stereocenter at C7, and a late-stage cascade reductive amination/cyclization to establish the highly strained caged ring system.

Cephalotane-type C20 diterpenoids from Cephalotaxus fortunei var. alpina.

Seventeen new cephalotane-type diterpenoids, fortalides A-Q (1-17), along with five known analogues, were isolated from the seeds of Cephalotaxus fortunei var. alpina. Their structures were determined by extensive spectroscopic methods, as well as electronic circular dichroism (ECD) and X-ray crystallographic data analyses. Some isolates exhibited unusual structural features that were first found in cephalotane-type diterpenoids, such as the occurrence of the 7-oxabicyclo[4.1.1]octane moiety in 14 and 15 and the cis-arrangement of 3-OH and Me-19 in 9. Besides, the antiplasmodial activity of these compounds was evaluated in this study.

Total Synthesis of (±)-Furanether A.

The first total synthesis of (±)-furanether A, which exhibits good antifeedant activity, has been concisely achieved in 13 linear steps. Notably, the key rigid tetracyclic skeleton containing a 1-methyl-8-oxabicyclo[3.2.1]octane moiety with two vicinal quaternary carbon centers was rapidly constructed in one step through a unique tandem C-H oxidation/oxa-[3,3] Cope rearrangement/aldol cyclization sequence.

Synthesis of Dumbbell‐Like DBATT Dimers**

AbstractTwo‐dimensional acenes are promising candidates for applications in single‐molecule spectroscopy due to the electronic properties caused by their zig‐zag periphery. However, synthetic access to their dimers remains unexplored because of low solubility and reduced stability. Herein we report a facile approach towards two‐dimensional acenes dimers on the example of 2.3,8.9‐dibenzanthanthrene (DBATT) connected via rigid linker. The exploitation of dehydrative π‐extension on the last step of the synthesis allows avoiding difficulties connected with cumbersome purification of low soluble products. The technique was shown to be applicable for the synthesis of DBATT dimers connected rigidly with conjugated and non‐conjugated linkers, containing alternating para‐phenylene and bicyclo[2.2.2]octane moieties.

A new route to BCD tricyclic fragment of C19-diterpenoid alkaloids via intramolecular Pauson-Khand reaction followed by anionic 1,2-migration rearrangement

A robust synthetic approach for the rapid assembly of the bridged tricyclic BCD ring system of C19-diterpenoid alkaloids bearing a characteristic hydroxy group on ring C has been developed. The synthesis features an efficient intramolecular Pauson-Khand reaction and an exclusive anionic 1,2-migration rearrangement to generate the unique bicyclo[3.2.1]octane moiety of the CD-ring on the seven-membered B-ring.

Six new degraded steroids including an unprecedented 4-methyl-androstane with oxabicyclo[3.2.1]octane moiety from Nodulisporium sp.

Abstract 4-Methyl-androstanes are a class of rare steroid. A chemical investigation on Nodulisporium sp. led to the isolation of an unprecedented 4-methyl-androstane (nodulisporandrostane A, 1) with an ether linkage between C-4 and C-9 forming an oxabicyclo[3.2.1]octane ring system, along with five biosynthetic related new androstanes (nodulisporandrostanes B–F, 2–6). Their structures were determined by detailed NMR analyses, X-ray crystallography, and NMR calculations. Based on the isolated compounds and our previous works, a plausible biosynthetic pathway of 1–6 was also proposed.

Novel approach to the synthesis and optical absorption properties of 2-(2-oxo-1,2-dihydro-3H-pyrrole-3-ylidene)malononitriles

Two approaches to the synthesis of 2-(2-oxo-5-aryl-1,2-dihydro-3H-pyrrol-3-ylidene)malononitriles (DCAA-pyrroles 1) were implemented. The first one was based on the transformation of 4-oxobutane-1,1,2,2-tetracarbonitriles 2 by the action of morpholine. The second approach was based on the reaction between protected form of 4-oxobutane-1,1,2,2-tetracarbonitriles 2 namely 2,7-dioxabicyclo[3.2.1]octane-4,4,5-tricarbonitriles 3 and morpholine. This approach involving sequential furan and pyran ring-opening of the 2,7-dioxabicyclo[3.2.1]octane moiety with further pyrrole ring-closure, resulted in a smoother formation of DCAA-pyrroles 1. The optical absorption properties of DCAA-pyrroles 1 were studied for the first time. The absorption maxima were observed in the range of 506–545 nm showing positive solvatochromism and dependence on the substituent in aryl moiety.

Divergent Total Synthesis of Euphoranginol C, Euphoranginone D, ent-Trachyloban-3β-ol, ent-Trachyloban-3-one, Excoecarin E, and ent-16α-Hydroxy-atisane-3-one.

A divergent synthetic approach to biogenetically related diterpenoids such as ent-kauranes, ent-trachylobanes, ent-beyerane, and ent-atisane has been developed. The unified synthetic route involves the De Mayo reaction to rapidly generate the bicyclo[3.2.1]-octane moiety of ent-kaurane. The key reactions also include bioinspired nucleophilic cyclopropanation generating the [3.2.1.02,7 ]-tricyclic core of ent-trachylobane and regioselective cyclopropane fragmentation furnishing ent-beyerane and ent-atisane through the nucleophilic attack and protonation of the cyclopropane ring. This strategy enables the asymmetric total syntheses of six diterpenoids from the commercially available geraniol.