A new and general route to 2-pyrrolylglycine, 2-pyrrolylalanine and homo-2-pyrrolylalanine derivatives

A general route to α-, β- and γ-pyrrole-branched α-amino acid derivatives has been developed, which featured a one-pot ring-closing metathesis and aromatization reaction as the key step.     

Adaptive robust control of Mecanum-wheeled mobile robot with uncertainties

This paper presents a novel implementation of an adaptive robust second-order sliding mode control (ARSSMC) on a mobile robot with four Mecanum wheels. Each wheel of the mobile robot is actuated by separate motors. It is the first time that higher-order sliding mode control method is implemented for the trajectory tracking control of Mecanum-wheeled mobile robot. Kinematic and dynamic modeling of the robot is done to derive an equation of motion in the presence of friction, external force disturbance, and uncertainties. In order to make the system robust, second-order sliding mode control law is derived. Further, adaptive laws are defined for adaptive estimation of switching gains. To check the tracking performance of the proposed controller, simulations are performed and comparisons of the obtained results are made with adaptive robust sliding mode control (ARSMC) and PID controller. In addition, a new and low-cost experimental approach is proposed to implement the proposed control law on a real robot. Experimental results prove that without compromising on the dynamics of the robot real-time implementation is possible in less computational time. The simulation and experimental results obtained confirms the superiority of ARSSMC over ARSMC and PID controller in terms of integral square error (ISE), integral absolute error (IAE), and integral time-weighted absolute error (ITAE), control energy and total variance (TV).     

Grob-type fragmentation of a carvone derived β-hydroxymesylate: application to the synthesis of chiral lavandulol derivatives

Grob-type fragmentation of the carvone derived diol-monosulphonate 5 has been utilised for the enantioselective synthesis of various lavandulol derivatives     

Facile Knoevenagel and Domino Knoevenagel/Michael Reactions Using Gel‐Entrapped Base Catalysts

An efficient method for Knoevenagel condensation of arenecarbaldehydes with active methylene compounds such as barbituric acid and Meldrum's acid in the presence of gel‐entrapped base catalysts is reported. The method has been extended to the one‐pot synthesis of arylmethylene‐bis[3‐hydroxycyclohex‐2‐en‐1‐one] derivatives from dimedone (=5,5‐dimethylcyclohexane‐1,3‐dione) and arenecarbaldehydes by using domino Knoevenagel/Michael reaction sequence.     

Microwave‐assisted synthesis of some 2,4‐thiazolidinedione derivatives

The condensation of 5‐[4′‐(2″‐halo‐ethoxy)benzylidenyl]‐2,4‐thiazolidinediones 2 when separately carried with different 2‐amino thiazoles 3 and different sulphanilamides 4 in DMF, using potassium hydroxide in the presence of a catalytic amount of a phase transfer catalyst, gave new 5‐[4′‐(4″‐aryl‐thiazol‐2″‐yl‐aminoethoxy)‐3′/5′‐substituted benzylidenyl]‐2,4‐thiazolidinediones 5 and 5‐[4′‐(2″/4″‐sulphonamidophenyl aminoethoxy)‐3′/5′‐substituted benzylidenyl]‐2,4‐thiazolidinediones 6 derivatives in good yields, respectively. The structures of all new compounds were established from analytical and spectral data. All the reaction sequences were carried under microwave irradiation, as an efficient tool. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:151–156, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20528     

Baker’s yeast: An efficient,green, and reusable biocatalyst for the one-pot synthesis of biologically important N-substituted decahydroacridine-1,8-dione derivatives

A green approach for one-pot three-component synthesis of N-substituted decahydroacridine-1,8-diones is offered for the first time using baker’s yeast (Saccharomyces cerevisiae) as a biocatalyst under ultrasonication. Due to growing safety and environmental concerns, enzymatic methods were constantly investigated as an attractive alternative to toxic and nonspecific chemical approaches. This method is relatively simple, efficient, inexpensive, and environment-friendly. The catalyst was recovered and reused and also the recyclability of baker’s yeast resulted in excellent yields of products without loss of any catalytic activity.     

A short route to the macrocyclic core of biaryl ether-based cyclopeptides

A new route based on an intramolecular Horner-Wadsworth-Emmons type olefination of amidophosphonates has been developed for the construction of a 17-membered macrocyclic scaffold related to some biologically important biaryl ether-based cyclic peptides.     

Sequential Two-Fold Claisen Rearrangement,One-Pot Ring-Closing Metathesis and Cross-Metathesis as a Route to Substituted Benzo[b]azepine-2-one,Benzo[b]azepine and Benzo[b]oxepine Derivatives

A synthetic protocol involving sequential use of three atom-economic processes viz. Claisen rearrangement, ring-closing metathesis and cross metathesis has been developed to access 7-substituted benzo[b]azepine and benzo[b]oxepine derivatives starting from appropriate aniline or phenol in good overall yield. A one-pot RCM-CM protocol has also been developed for the synthesis of benzazepine and benzoxepine derivatives.