Activation of glycosyl methylpropiolates by TfOH.

Activation of glycosyl methylpropiolates by TfOH was investigated. Armed and superarmed glycosyl donors can be activated by use of 0.2 equivalent TfOH whereas 1.0 equivalent of TfOH was required for the activation of the disarmed glycosyl donors. All the glycosidations gave very good yields. The method is suitable for synthesis of glycosides and disaccharides and it may result in the hydrolysis of the interglycosidic bond if the sugar at the non-reducing end is armed or superarmed. These problems are not seen when gold-catalyzed activation procedures are invoked for the activation of glycosyl alkynoates.

His1-tagged DM or DDM detergent micelles are reversibly conjugated by nickel ions.

Specific conjugation of decyl ß-D-maltoside (DM) or dodecyl ß-D-maltoside (DDM) detergent micelles is accomplished between pH 7.0-8.5 in the presence of an amphiphilic analog of the amino acid histidine, bound to a 10-carbon hydrocarbon chain (His1-C10) and Ni2+ ions. Following addition of 10-15 wt% PEG-6000 as precipitant, phase separation in the form of oil-rich globules (30-600 µm) is observed by light microscopy. Other divalent cations: Zn2+, Fe2+, Cu2+ lead to dark precipitates rather than colorless globules; while Mg2+, Ca2+ do not promote any phase separation at all. Even in the absence of precipitant, dynamic light scattering (DLS) measurements demonstrate that DM micelles (hydrodynamic size ~ 6 nm) or DDM micelles (8 nm) self-associate into larger particles (9 nm and 411 nm for DM; 10 nm and 982 nm for DDM) in the presence of His1-C10 and nickel ions. Micellar conjugation is partially reversible in the presence of water soluble 50 mM EDTA, histidine or imidazole chelators. Cryo-transmission electron microscopy (cryo-TEM) imaging revealed the formation of non-uniformly dense detergent aggregates for both DM and DDM micelles in the presence of precipitant. The possible utility of such His1-tagged DM or DDM micelles for promoting crystallization of integral membrane proteins is discussed.

Synthesis of Spirolactones and Functionalized Benzofurans via Addition of 3-Sulfonylphthalides to 2-Formylaryl Triflates and Conversion to Benzofuroisocoumarins.

A convenient protocol for the synthesis of spirobenzofuran-isobenzofurans and substituted benzofurans via a modified Hauser-Kraus reaction of 3-sulfonylphthalide with 2-formylaryl triflates is reported here. The initial reaction involved 1,2-addition of phthalide to the formyl group and intramolecular cyclization via substitution of triflate followed by a cascade of rearrangements leading to spirolactone or benzofuran derivatives. The electronic nature of substituents on aryl triflates affected the course and outcome of the reaction. The mechanism was supported by successful characterization of one of the intermediates by mass spectrometry. A medicinally relevant influenza virus type B inhibitor, benzofuroisocoumarin, was synthesized in a single step from the spiro compound, thus demonstrating the synthetic utility of our methodology.

Reactions of Sulfonylphthalide with Diverse Activated Imines for the Synthesis of Enaminophthalides, Spiro-isoquinolinones, and Homalicine Natural Products.

The reactivity of the Hauser-Kraus (H-K) donor, 3-sulfonylphthalide, with various activated imines under basic conditions is demonstrated. The reaction of 3-sulfonylphthalide with Boc-protected aldimine provides a rapid access to 1,2-imine adducts and alkylidenephthalides depending upon the stoichiometry of the base. The alkylidenephthalides could be transformed to ketophthalides, a new class of phthalides, on acid hydrolysis, which upon reductive cyclization using Zn/AcOH afforded the natural product homalicine. On the contrary, the Boc-protected isatinimines undergo an efficient H-K annulation to provide spiro-isoquinolinone-oxindoles in excellent yields. However, the corresponding conjugated ketimines afforded Michael adducts, which were converted to the corresponding alkylidenephthalides under TBAF conditions.

Synthesis of ß-triazolylenones via metal-free desulfonylative alkylation of N-tosyl-1,2,3-triazoles.

Desulfonylative alkylation of N-tosyl-1,2,3-triazoles under metal-free conditions leading to ß-triazolylenones is reported here. The present study encompasses the synthesis of triazoles with a new substitution pattern in a single step from cyclic 1,3-dicarbonyl compounds and N-tosyl triazole in moderate to high yields. Our synthesis takes place with complete regioselectivity as confirmed by crystallographic analysis which is rationalized by a suitable mechanistic proposal. This method provides an efficient, versatile and straightforward strategy towards the synthesis of new functionalized 1,2,3-triazoles.

Stereoselective Synthesis of Tri- and Tetrasubstituted Olefins via 1,6-Additions of Diazo Compounds and Their Precursors to p-Quinone Methides.

Reactions of para-quinone methides (p-QMs) with α-diazo-ß-ketosulfones and their corresponding esters as well as simple ß-dicarbonyl compounds and ß-ketosulfones have been carried out under basic conditions. While the reaction of diazosulfone with p-QMs afforded trisubstituted olefins via deacylative 1,6-addition and elimination, α-diazo-ß-ketoesters and various active methylene compounds such as 1,3-dicarbonyls and ß-ketosulfones afforded tetrasubstituted olefins via 1,6-addition and aerial oxidation. These simple, environmentally benign, and mechanistically diverse protocols provided the products in moderate to excellent yields and selectivities.

Evaluation of geriatric changes in dogs.

AIM: The present study has been envisaged to ascertain the old age for critical management of geriatric dogs considering the parameters of externally visible changes, haemato-biochemical alterations and urine analysis in geriatric dogs approaching senility. MATERIALS AND METHODS: The study was undertaken in the Department of Veterinary Pathology in collaboration with Teaching Veterinary Clinic complex spanning a period of 1 year. For screening of geriatric dogs, standard geriatric age chart of different breeds was followed. The external characteristics such as hair coat texture, dental wear and tear, skin texture and glaucoma were taken as a marker of old age. Haematology, serum biochemistry and urine analysis were also included in the study. RESULTS: External visible changes like greying of hair, dull appearance of hair coat, glaucoma, osteoarthritis, dental wear and tear were commonly encountered in the aged dogs. The haemoglobin, total erythrocyte count and packed cell volume showed a decreasing trend in the geriatric groups. Biochemical values like total protein, albumin, calcium level showed a decreasing trend while urea level with an increasing trend in geriatric dogs without any much alteration in serum glutamic-oxaloacetic transaminse, serum glutamic-pyruvate transaminase, cholesterol and creatinine. Physical examination of urine revealed yellow, amber, red, deep red color with turbidity and higher specific gravity. Chemical examination revealed presence of protein, glucose, ketone bodies, blood and bilirubin on some cases. The culture and sensitivity test of the urine samples revealed presence of bacteria with sensitive and resistance to some antibiotics. CONCLUSION: External visible changes are still the golden standard of determining the old age in dogs. Haemato-biochemical evaluation can be useful for correlating with the pathophysiological status of the animal. Biochemical analysis of urine can be employed rightly as kidney dysfunction is being major geriatric problem. Anaemia, jaundice, nephritis, hepatitis are the most common findings considered during old age.

X-gal staining of canine skin tissues: A technique with multiple possible applications.

BACKGROUND: Estimation of ß-galactosidase (ßgal) activity in human cells and tissues indicate its possible use as a marker of senescence. OBJECTIVES: This study was done to detect senescence-associated ßgal (SA-ßgal) activity in canine skin tissue by using its substrate 5-bromo-4-chloro-3-indolyl ß-D-galactosidase (X-gal). MATERIALS AND METHODS: Skin samples were collected through rapid necropsy process. The X-gal staining was done by altering different factors of the staining procedure like pH of the reagents and incubation time. Further, effect of tissue preservation procedure was also evaluated. RESULTS: Typical X-gal staining was detected in old dogs' skin samples and it was detectable both at pH 6 and pH 7.3. The cells present in the inner lining of the hair follicles and sebaceous glands are the major cells that have high SA-ßgal activity. The X-gal staining intensity was more prominent in tissues preserved in liquid nitrogen at -196°C than in -80°C freezer. Prolonged incubation period increased the intensity of staining. CONCLUSIONS: This study indicates possibility of X-gal staining in canine tissues and opens an avenue for further in-depth studies that might be useful for different research and clinical studies like determination of dog's approximate age.