1,821 research outputs found
Dehydroabietic acid
The title compound [systematic name: (1R,4aS,10aR)-7-isopropyl-1,4a-dimethyl-1,2,3,4,4a,9,10,10a-octahydrophenanthrene-1-carboxylic acid], C20H28O2, has been isolated from disproportionated rosin which is obtained by isomerizing gum rosin with a Pd-C catalyst.. Two crystallographically independent molecules exist in the asymmetric unit. In each molecule, there are three six-membered rings, which adopt planar, half-chair and chair conformations. The two cyclohexane rings form a trans ring junction with the two methyl groups in axial positions. The crystal structure is stabilized by intermolecular O—H⋯O hydrogen bonds
7-Isopropyl-1,4a-dimethyl-1,2,3,4,4a,5,6,7,8,9,10,10a-dodecahydrophenanthrene-1-carboxylic acid
The title compound, C20H32O2, has been isolated from hydrogenated rosin. There are two independent molecules in the asymmetric unit. In each molecule, the cyclohexane ring assumes a chair conformation, while the two cyclohexene rings adopt half-chair and envelope conformations. Intermolecular O—H⋯O hydrogen bonding between carboxyl groups links pairs of independent molecules into dimers
BOURNE: Bootstrapped Self-supervised Learning Framework for Unified Graph Anomaly Detection
Graph anomaly detection (GAD) has gained increasing attention in recent years
due to its critical application in a wide range of domains, such as social
networks, financial risk management, and traffic analysis. Existing GAD methods
can be categorized into node and edge anomaly detection models based on the
type of graph objects being detected. However, these methods typically treat
node and edge anomalies as separate tasks, overlooking their associations and
frequent co-occurrences in real-world graphs. As a result, they fail to
leverage the complementary information provided by node and edge anomalies for
mutual detection. Additionally, state-of-the-art GAD methods, such as CoLA and
SL-GAD, heavily rely on negative pair sampling in contrastive learning, which
incurs high computational costs, hindering their scalability to large graphs.
To address these limitations, we propose a novel unified graph anomaly
detection framework based on bootstrapped self-supervised learning (named
BOURNE). We extract a subgraph (graph view) centered on each target node as
node context and transform it into a dual hypergraph (hypergraph view) as edge
context. These views are encoded using graph and hypergraph neural networks to
capture the representations of nodes, edges, and their associated contexts. By
swapping the context embeddings between nodes and edges and measuring the
agreement in the embedding space, we enable the mutual detection of node and
edge anomalies. Furthermore, we adopt a bootstrapped training strategy that
eliminates the need for negative sampling, enabling BOURNE to handle large
graphs efficiently. Extensive experiments conducted on six benchmark datasets
demonstrate the superior effectiveness and efficiency of BOURNE in detecting
both node and edge anomalies
2-Hydroxy-6,6-dimethylbicyclo[3.1.1]heptane-2-carboxylic acid
The title compound, C10H16O3, with a bicyclo[3.1.1]heptane unit, was obtained by oxidation of β-pinene. The asymmetric unit contains two independent molecules with similar geometry: the six-membered rings in both molecules adopt envelope conformations. In the crystal, the independent molecules exist as O—H⋯O hydrogen-bonded dimers. The dimers are linked into helical chains along the b axis by O—H⋯O hydrogen bonds
15-Hydroxyethyl-19-isopropyl-5,9-dimethyl-14,16-dioxo-15-azapentacyclo[10.5.2.01,10.04,9.013,17]nonadec-18-ene-5-carboxylic acid
The title compound, C26H37NO5, which was synthesized from monoethanolamine and maleopimaric acid, consists of two fused and unbridged cyclohexane rings. They form a trans ring junction with a chair conformation. The two methyl groups are in axial positions. In the crystal, intermolecular O—H⋯O hydrogen bonds link adjacent molecules into a layer structure. Two C—H⋯O interactions are also present
2-[(1S,3S)-3-Acetyl-2,2-dimethylcyclobutyl]-N-(m-tolyl)acetamide
The title compound, C17H23NO2, contains two chiral centres and was synthesized from 2-(3-acetyl-2,2-dimethylcyclobutyl)acetic acid and m-toluidine. The cyclobutane ring is not flat but flexed as though folded from the dimethyl-substituted C atom to the unsubstituted C atom, with a dihedral angle of 25.9°. The crystal structure is stabilized by N—H⋯O and C—H⋯O hydrogen-bonding interactions
16-Isopropyl-5,9-dimethyltetracyclo[10.2.2.01,10.04,9]hexadec-15-ene-5,14-dimethanol
The title compound, C23H38O2, a tetracyclo[10.2.2.01,10.04,9] hexadecane structure, crystallized with four independent molecules in the asymmetric unit. In the crystal, these independent molecules are linked by O—H⋯O hydrogen bonds, forming a polymeric chain propagating in [100
SYNTHESIS OF CYCLOBUTANE ANALOGUES
2-(3-Acetyl-2,2-dimethylcyclobutyl)acetic acid (pinonic acid) was synthesized using α-pinene as raw material and potassium permanganate as oxidant. This compound reacted with substituted aniline to produce eight kinds of derivatives with cyclobutane moiety. The yields of the cyclobutane analogues ranged from 24.9 to 78.2 %.
KEY WORDS: Cyclobutane analogues, Pinonic acid, Oxidation
Bull. Chem. Soc. Ethiop. 2009, 23(1), 135-139
N-Benzylidenenordehydroabietylamine
The title compound [systematic name: (1R,4aS,10aR,E)-N-benzylidene-7-isopropyl-1,4a-dimethyl-1,2,3,4,4a,9,10,10a-octahydrophenanthren-1-amine], C26H33N, has been synthesized from nor-dehydroabietylamine and benzaldehyde. The two cyclohexane rings form a trans ring junction with classic chair and half-chair conformations, respectively, the two methyl groups are on the same side of tricyclic hydrophenanthrene structure. The dihedral angle between two benzene rings is 44.2 (4)°. The C=N bond is in an E configuration
16-Isopropyl-5,9-dimethyltetracyclo[10.2.2.01,10.04,9]hexadec-15-ene-5,13,14-tricarboxylic acid dimethylformamide disolvate
The title compound, C24H34O6·2C3H7NO, which was isolated from fumaric-modified rosin, has four asymmetrically fused six-membered rings and three carboxylic acid substituents. It contains two fused and unbridged cyclohexane rings, which form a trans ring junction with a chair conformation. The asymmetric unit includes one fumaropimaric acid and two dimethylformamide molecules. The crystal structure is stabilized through intermolecular O—H⋯O hydrogen bonds between dimethylformamide and fumaropimaric acid
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