New syntheses of protoberberines: Cycloaddition and carbanionic methodology leading to the production of highly enantioselective products

New synthetic methods are explored for the synthesis of protoberberines using carbanionimine (CAI) cycloaddition, aza Diels-Alder (DA) cycloaddition.. Protoberberine alkaloids are widely distributed in numerous plant families, and commonly found as active components in many folklore medicines in Asia, Europe and North America. Due to their broad diversity of biological activities, there are great efforts about chemical, biogenetic and enzymatic synthesis, transformation, pharmacology, and culture development studies of these alkaloids. In this thesis, new synthetic methods are explored for the synthesis of protoberberines using the following approaches a) carbanionimine (CAI) cycloaddition, b) aza Diels-Alder (DA) cycloaddition. The structure elucidation of products using various analytical techniques, such as IR, UV-vis., MS, NMR and X-ray, are broadly discussed. Detailed stereostructure and conformation analysis have been studied using various one and two dimensional NMR techniques, which show great advantage for structure analysis in the liquid state, and give the consistent conclusion as the solid state structure as determined by the single crystal X-ray diffraction method. The carbanion-cyclic imine approach has been most successful in the synthesis of protoberberines, which contain a four-ring system (ABCD). Cycloaddition of 3,4-dihydroisoquinoline (DHIQ, eg A-I) with phthalide anion (eg A-2) gives stereo and regia selective 13-hydroxy protoberberines (eg A-3) with single diastereomers observed and isolated, which are transformed to various functionalised derivatives. The novel reaction of 3-methoxyphthalide anion (A-4) with DHIQ, where a 2+1 adduct (A-6) is formed, is broadly studied. The mechanisms are studied in details and highly suggestive via tandem nucleophilic condensation of the anion, in which the 8,13-dioxo intermediate (eg A-5) plays an important role. The geometry change due to the replace of angular 13a-H with methyl group accounts for the different facial selectivity of 13-keto to nucleophiles in A-5a A-5b. These are supported by theoretical AMl calculation and Surface Probe Analysis on model compounds (A-8). The phthalide anion-acyclic imine approach has been used to provide open chain products (eg A-10 and A-11). NMR and AMl calculation prove trans stereochemistry of major isomers (eg A-10). The conclusion is in contrast to previous assignments by MacLean, Cushman, and Prager on similar compounds. The direct asymmetric synthesis is also explored by using a chiral o-toluamide anion (eg A-12) instead of a phthalide counterpart. A series of chiral amine auxiliary agents have been studied and the tertiary o-toluamide with a bulky cyclohexyl group in addition to the chiral substituent on the amide nitrogen atom (A-12) gives the highest enantioselectivity (>96% ee). This approach established a new, fast entry to both enantiomers of protoberberines and exhibits predictable regiochemistry. This is an obvious advantage in all anion-imine cycloaddition reactions in our study and others. DA methodology is also studied, however only the reaction between DHIQ (AB synthon) and phthalazine (A-14, CD synthon) works. This reaction is the first example of aza DA reaction with phthalazine as an aza diene with an aza dienophile. The other AB+CD approaches with DHIQ (AB) as dienophile allowed to react with different dienes (CD), such as isobenzofuran and cyclopentadienone, do not give any adducts under thermal, Lewis acid catalyst or high pressure conditions. While the first step of an AB+C+D approach which involves sequential DA reaction of DHIQ with s-tetrazine (A-16) was successful, the second step involving benzyne or cyclic enamine cycloaddition failed

The impact of IFRS on accounting quality in a regulated market : an empirical study of China

As more countries consider the adoption of International Financial Reporting Standards (IFRS) that are based on practices prevalent in the English-speaking countries with free markets, it’s increasingly important to understand the impact of IFRS on countries of different institutional, economic, and political environments. This article reports a study that examines the impact of IFRS on accounting quality in a regulated market, China, where new substantially IFRS-convergent accounting standards became mandatory for listed firms in 2007. Accounting quality is examined for the period 2005 to 2008 with only firms mandated to follow the new standards. The empirical results generally indicate that accounting quality improved with decreased earnings management and increased value relevance of accounting measures in China since 2007. Firms audited by the Big Four are expected to have higher quality before the standard change evidenced quality improvement to a smaller extent. Further analysis shows that such changes are less likely to result from changes in economic conditions but from the changes of the standards. Through the analysis of China’s adoption of the new substantially IFRS-convergent standards, the study provides direct evidence on the question of whether IFRS can be relevant to markets that are still disciplined mainly by regulators rather than by market mechanisms

Crystal structure of (3s*,4s*)-4-hydroxy-2-(2'methoxyethyl)-3-phenyl-3-4-dihydroisoquinol-1(2h)-one, c18h19no3

C18H19NO3, monoclinic, P121/n1 (No. 14), a+8.454(6) A, b=13.123(3) A, c=14.698(3)A,P=104.85(3)o, V=1576.2 A3, Z=4, Rgt(F)=0.062, wRref(F2)=0.184, T=293 K. Source of material. This compound was prepared by the method described in the previous paper [1] but replacing the 3,4-dihydroisoquinoline with N(2'-methoxyethyl)-bezaldimine (0.815 g, 5mmol). Following chromatography, the product was isolated and recrystallised from ethanol in 13% yield (mp 407 K - 407.5 K). The product was characterised by a 3J coupling between the cis-related protons H-3 and H-4 of 6.9 Hz[2]. Experimental details The H atoms were placed in their geometrically calculated positions and included in the final refinement in the riding model approximation

Crystal structure of (13s*,13ar*)-2,3-dimethoxy-13-hydroxy-13a-menthyl-8-oxo-5,6,13,13a-tetrahydro-8h-dibenzo[a,g]quinolizine, c20h21no4

C2oH21N04, monoclinic, PI21/c1 (No, 14), a = 7.521(2) A, b =23.257(2) ,c =9.784(2) A, f3 =95.57(2)°, V =1703.3 A, Z =4, Rgt(F) =0.060, 11·-RrcdF2) =0.183, T= 293 K

Federated Deep Reinforcement Learning-Based Spectrum Access Algorithm With Warranty Contract in Intelligent Transportation Systems

Cognitive radio (CR) provides an effective solution to meet the huge bandwidth requirements in intelligent transportation systems (ITS), which enables secondary users (SUs) to access the idle spectrum of the primary users (PUs). However, the high mobility of users and real-time service requirements result in the additional transmission collisions and interference, which degrades the spectrum access rate and the quality of service (QoS) of users in ITS. This paper proposes a spectrum access algorithm (Feilin) based on federated deep reinforcement learning (FDRL) to improve spectrum access rate, which maximizes the QoS reward function with considering the hybrid benefits of delay, transmission power and utility of SUs. To guarantee the utility of SUs, the warranty contract is designed for SUs to obtain compensation for data transmission failure, which promotes SUs to compete for more spectrum resources. To meet the real-time requirements and improve QoS in ITS, a spectrum access model called FDQN-W is proposed based on federated deep Q-network (DQN), which adopts the asynchronous federated weighted learning algorithm (AFWLA) to share and update the weights of DQN in multiple agents to decrease time cost and accelerate the convergence. Detailed simulation results show that, in the multiuser scenario, compared with the existing methods, the proposed algorithm Feilin increases the spectrum access success rate by 15.1%, and reduces the collision rate with SUs and the collision rate with PUs by 46.4% and 6.8%, respectively

A Lightweight and Conditional Privacy-Preserving Authenticated Key Agreement Scheme with Multi-TA Model for Fog-Based VANETs

Recently, the fog computing concept has been introduced into vehicular ad-hoc networks (VANETs) to formulate fog-based VANETs. Since the communication channels between vehicles and fog nodes are open and insecure, it is necessary to construct an authenticated key agreement (AKA) scheme for securing the channels. The existing AKA schemes have two main deficiencies. One is that the computational and communication overhead are not low enough to satisfy the requirements of delay-sensitive applications. The other is that the multi-Trusted-Authority (multi-TA) model has not been considered. To solve the deficiencies, we propose a lightweight and conditional privacy-preserving AKA scheme, where the main steps are designed with symmetric cryptography methods. The design can reduce the computational and communication overhead of the AKA process. Additionally, we consider the multi-TA model in the AKA process to solve the single-point-of-failure issue. By integrating Cuckoo filter into the multi-TA model, the secrecy of real identities of legal vehicles is guaranteed and the identity revocation function for illegal vehicles is supported in the AKA process. The security proof and analysis show that our proposed scheme satisfies the essential security and privacy requirements of VANETs. The performance analysis shows that our proposed scheme outperforms other related and represented schemes

Energy efficient heuristic algorithm for task mapping on shared-memory heterogeneous MPSoCs

Existing research mostly reduce mapping time and inter-processors communication energy of the multiprocessor system-on-chips (MPSoCs). Unlike other approaches in this paper we have explored energy efficient task mapping on shared-memory heterogeneous MPSoCs considering the energy performance profile of the processors. We propose mitosis heterogeneous-genetic algorithm (MH-GA) for energy aware task mapping on DVFS-enabled processors in order to maximally exploit the inherent heterogeneity in the MPSoC platform while satisfying the application deadline restriction. The proposed heuristic mapping approach has an integrated list scheduler that assigns priority to the tasks with lower deadlines. The experiments are conducted on 4 synthetic and 4 real-world task graphs (TGs) acquired from embedded systems synthesis benchmarks (E3S). The experimental results are compared with the greedy algorithm and our proposed heuristic algorithm achieves maximum energy efficiency of ~53.2% while reduces the average energy consumption ~21.5%

A novel meta-heuristic for green computing on VFI-NoC-HMPSoCs

The number of processors has increased significantly on multiprocessor system therefore, Voltage Frequency Island (VFI) recently adopted for effective energy management mechanism in the large scale multiprocessor chip designs. Heterogeneous VFI, Network-on-Chip (NoC) based Multiprocessor System-on-Chips (MPSoCs) i.e. VFI-NoC-HMPSoCs are widely adopted in computational extensive applications due to their higher performance and an exceptional Quality-of-Service (QoS). Proper task scheduling using search-based algorithms on multiprocessor architectures can significantly improve the performance and energy-efficiency of a battery-constrained embedded system. In this paper, unlike the existing population-based optimization algorithms, we propose a novel population-based algorithm called ARSH-FATI that can dynamically switch between explorative and exploitative search modes at run-time for performance trade-off. We also developed a communication contention-aware Earliest Edge Consistent Deadline First (EECDF) scheduling algorithm. Our static scheduler ARHS-FATI collectively performs task mapping and ordering. Consequently, its performance is superior to the existing state-of-the-art approach proposed for homogeneous VFI based NoC-MPSoCs. We conducted the experiments on 8 real benchmarks adopted from Embedded Systems Synthesis Benchmarks (E3S). Our static scheduling approach ARSH-FATI outperformed state-of-the-art technique and achieved an average energy-efficiency of 15% and 20% over CA-TMES-Search and CA-TMES-Quick respectively

Assessing Profit of Prediction for SDN controllers load balancing

Software-defined networking (SDN) provides programmable control and centralized management in data centers, making it a popular architecture. The large scale of networks has required to propose the geographical distribution of logically centralized control plane to achieve scalability and reliability. For solving the load imbalance among multiple controllers associated with the statically configured control plane, a switch migration mechanism is proposed to admit dynamic load balancing. Many studies have been carried out for solving the control plane load balancing problem based on the switch migration mechanism. However, previous studies focus on migrating the switches when the controllers are overloaded, thereby, wasting time in the switch migration phase and resulting in high latency. To address these problems, we propose the Assessing Profit Of Prediction (APOP) scheme, a load-balancing strategy in the multiple-controllers control plane based on the overloaded state prediction and profit assessment. We introduce Taylor's formula to predict the flow change in the network and assess the profit of migrating switches in advance, in order to decrease the migration time and minimize the harmful effects during the migration phase. The result of simulation experiments shows that our scheme performs effectively in reducing the migration cost in control plane load balancing

PA-CRT: Chinese Remainder Theorem Based Conditional Privacy-preserving Authentication Scheme in Vehicular Ad-hoc Networks

Existing security and identity-based vehicular communication protocols used in Vehicular Ad-hoc Networks (VANETs) to achieve conditional privacy-preserving mostly rely on an ideal hardware device called tamper-proof device (TPD) equipped in vehicles. Achieving fast authentication during the message verification process is usually challenging in such strategies and further they suffer performance constraints from resulting overheads. To address such challenges, this paper proposes a novel Chinese remainder theorem (CRT)-based conditional privacy-preserving authentication scheme for securing vehicular authentication. The proposed protocol only requires realistic TPDs, and eliminates the need for pre-loading the master key onto the vehicle's TPDs. Chinese remainder theorem can dynamically assist the trusted authorities (TAs) whilst generating and broadcasting new group keys to the vehicles in the network. The proposed scheme solves the leakage problem during side channel attacks, and ensures higher level of security for the entire system. In addition, the proposed scheme avoids using the bilinear pairing operation and map-to-point hash operation during the authentication process, which helps achieving faster verification even under increasing number of signature. Moreover, the security analysis shows that our proposed scheme is secure under the random oracle model and the performance analysis shows that our proposed scheme is efficient in reducing computation and communication overheads