Prabhakar Sripadi

One-pot synthesis of functionalized isoxazole–thiolane hybrids via Knoevenagel condensation and domino sulfa-1,6-Michael/intramolecular vinylogous Henry reactions

One-pot synthesis of highly functionalized tetrahydrothiophene (thiolane) derivatives conjugated with biologically useful isooxazole are reported via the Knoevenagel condensation followed by domino sulfa-1,6-Michael/intramolecular vinylogous Henry reactions of aldehydes, 1,4-dithiane-2,5-diol and 3,5-dimethyl-4-nitroisoxazole. From the base and solvent screening, it was found that piperidine (30 mol%) and ethanol are the most suitable conditions giving the desired products with >95% yields in 2–2.5 h overall reaction time.

Hypoiodous acid-catalyzed regioselective geminal addition of methanol to vinylarenes: synthesis of anti-Markovnikov methyl acetals

A novel metal-free, catalytic geminal dimethoxylation of vinylarenes based on in situ generated HOI species from iodide salt and oxone is reported. The preliminary mechanistic investigations suggest that the key factor for achieving the anti-Markovnikov regioselectivity is the semipinacol rearrangement of an iodo functionalized intermediate, which is confirmed by an isotope labeling experiment. In addition, the reaction involves the de-iodination of a co-iodo intermediate via its oxidation to hypervalent iodine species rather than a common iodide abstraction by electrophiles. The HRESI-MS studies support the conversion of monovalent iodine containing intermediates to trivalent iodine intermediates during the catalytic conversion of aromatic alkenes into the corresponding terminal acetals.

Prostate Cancer Associated Lipid Signatures in Serum Studied by ESI-Tandem Mass Spectrometryas Potential New Biomarkers

Prostate cancer (PCa) is one amongst the most common cancersin western men. Incidence rate ofPCa is on the rise worldwide. The present study deals with theserum lipidome profiling of patients diagnosed with PCa to identify potential new biomarkers. We employed ESI-MS/MS and GC-MS for identification of significantly altered lipids in cancer patient’s serum compared to controls. Lipidomic data revealed 24 lipids are significantly altered in cancer patinet’s serum (n = 18) compared to normal (n = 18) with no history of PCa. By using hierarchical clustering and principal component analysis (PCA) we could clearly separate cancer patients from control group. Correlation and partition analysis along with Formal Concept Analysis (FCA) have identified that PC (39:6) and FA (22:3) could classify samples with higher certainty. Both the lipids, PC (39:6) and FA (22:3) could influence the cataloging of patients with 100% sensitivity (all 18 control samples are classified correctly) and 77.7% specificity (of 18 tumor samples 4 samples are misclassified) with p-value of 1.612×10−6 in Fischer’s exact test. Further, we performed GC-MS to denote fatty acids altered in PCa patients and found that alpha-linolenic acid (ALA) levels are altered in PCa. We also performed an in vitro proliferation assay to determine the effect of ALA in survival of classical human PCa cell lines LNCaP and PC3. We hereby report that the altered lipids PC (39:6) and FA (22:3) offer a new set of biomarkers in addition to the existing diagnostic tests that could significantly improve sensitivity and specificity in PCa diagnosis.

Insights into the Morita–Baylis–Hillman reaction of isomeric dibenzofuran carbaldehydes: a theoretical and mass spectral study

We herein report the faster Morita–Baylis–Hillman (MBH) reaction of dibenzofuran-4-carbaldehyde (2) than that of its isomer, dibenzofuran-2-carbaldehyde (1), with different activated olefins in the presence of DABCO as the base catalyst. We observed that there is no significant effect of the solvent (methanol) on the reaction rates. In situ mass spectrometry experiments and computational studies were applied to understand the role of the reaction intermediates and their structure implications. MS data revealed that the zwitterionic intermediate obtained from 2 is more stable than that obtained from 1. Computational studies were performed for the gas as well as solvent phase reactions at the mPW1K/6-31 + G(d,p) level. In accordance with the experimental results, aldehyde 2 is found to be more reactive compared to 1. The results are in accordance with McQuades proposal of the MBH mechanism, wherein the second equivalent of aldehyde plays a key role in the proton migration step during the course of the reaction in the absence of methanol solvent.

Identification and characterization of stress degradants of lacosamide by LC–MS and ESI-Q-TOF-MS/MS: Development and validation of a stability indicating RP-HPLC method

The current study dealt with the degradation behavior of lacosamide (LAC) under ICH prescribed stress conditions. LAC was found to be labile under acid and base hydrolytic stress conditions, while it was stable to neutral hydrolytic, oxidative, photolytic and thermal stress. In total, seven degradation products (DPs) were formed, which were separated on a C18 column using a stability-indicating method. LC-MS analyses indicated that one of the DPs had the same molecular mass as that of the drug. Structural characterization of DPs was carried out using ESI-Q-TOF-MS/MS technique. The degradation pathways and mechanisms of degradation of the drug were delineated by carrying out the degradation in different co-solvents viz. methanol, deuterated methanol, ethanol, 1-propanol and acetonitrile. The developed LC method was validated for the determination of related substances and assay of LAC as per ICH guidelines. This study demonstrates a comprehensive approach of LAC degradation studies during its development phase.

Cloning of fatty acid desaturase-coding sequence ( Lufad3 ) from flax and its functional validation in rice

Flax contains very high levels of alpha-linolenic acid (57%) and a fatty acid desaturase 3-coding sequence (Lufad3) of flax has been amplified from the RNA isolated from developing seeds. The deduced amino acid sequence of LuFAD3 showed the presence of three histidine motifs, six membrane spanning domains and an endoplasmic reticulum (ER) retention signal KSK, indicating its plausible localization into the ER. Flax is not amenable for genetic transformation and not suitable for functional validation of Lufad3 gene. Hence, rice with well-developed genetic transformation has been selected as heterologous host system. Coding sequence of Lufad3 driven by maize Ubi1 promoter has been introduced into indica rice by Agrobacterium tumefaciens-mediated genetic transformation. Southern analysis of putative transformants (T0) revealed signals at variable lengths at >5 kbp indicating random integration of transgene into the genomes of different transformants. The Mendelian segregation observed for selectable marker gene hyg in both T1 and T2 generations confirmed stable inheritance and single-site integration of transgenes. As compared to untransformed control (UC), homozygous transgenic rice expressing Lufad3 showed higher levels of essential α-linolenic acid in leaves and seeds validating its functionality.