Mild and chemoselective lactone ring-opening with (TMS)ONa. Mechanistic studies and application to sweroside derivatives

Mild and chemoselective opening of lactones with sodium trimethylsilanolate in high yields and aprotic solvents is described. Kinetic studies demonstrate that the B(Ac)2 mechanistic pathway is followed. Nucleophilic attack of silanolate onto the carbonyl of the lactone moiety is the rate-determining step. NaOH present as an impurity accelerates the reaction. The method was further applied to the base-sensitive and stable lactones derived from highly functionalized iridoid derivatives.

Amide formation in one pot from carboxylic acids and amines via carboxyl and sulfinyl mixed anhydrides

An efficient method has been developed for the preparation of yet unknown acyclic mixed anhydrides of carboxylic and sulfinic acids. Sterically hindered 2-methylbut-3-ene-2-sulfinyl carboxylates add primary and secondary amines preferentially onto the carbonyl moieties realizing a new method for the one-pot preparation of carboxamides. It uses 1:1 mixtures of carboxylic acids and amines without a base, requires no excess of reagents, and liberates only volatile coproducts. Protected di- and tripeptides have been prepared in solution without epimerization by application of this method.

Intermolecular insertion of ethylene and octene into a palladium-amide bond. Spectroscopic evidence for an ethylene amido intermediate

We report a series of palladium diarylamido complexes containing a cyclometalated phosphine ligand and a coordinated THF that form enamine products from migratory insertion of ethylene and octene into the metal-nitrogen bond. The reactions of these complexes were sensitive to the electronic properties of the diarylamido group. The complex with the more electron-donating amido ligand reacted nearly 2 orders of magnitude faster than the complex with the least electron-donating amido group. The mechanism of the reactions with alkenes involves exchange of olefin for THF, as revealed by the positive order of the reaction in alkene and inverse order in the concentration of THF. A syn-aminopalladation that would result from migratory insertion was revealed by the stereochemistry of the enamine product resulting from reaction with cis-ethylene-d(2). Finally, a three-coordinate THF-free species was isolated from a synthesis of the amido complex in aromatic solvents, and spectroscopic evidence for an ethylene amido species was gained, in part by the addition of H(2)(13)C=(13)CH(2) to the three-coordinate amido complex at -100 degrees C.

Direct, intermolecular, enantioselective, iridium-catalyzed allylation of carbamates to form carbamate-protected, branched allylic amines

The direct reaction between carbamates and achiral allylic carbonates to form branched, conveniently protected primary allylic amines with high regioselectivity and enantioselectivity is reported. This process occurs without base or with 0.5 equiv K(3)PO(4) in the presence of a metalacyclic iridium catalyst containing a labile ethylene ligand. The reactions of aryl-, heteroaryl-, and alkyl-substituted allylic carbonates with BocNH(2), FmocNH(2), CbzNH(2), TrocNH(2), TeocNH(2), and 2-oxazolidinone occur in good yields, with high selectivity for the branched isomer and high enantioselectivities (98% average ee).

[Assessment of perioperative fluid balance]

Careful assessment of the fluid balance is required in the perioperative period since appropriate fluid therapy is essential for successful patient's outcome. Haemodynamic monitoring allows understanding the physiology of the circulation and changes of fluid balance in the perioperative period. This is diagnostic aid and guide for fluid replacement therapy. Patient's volume status is frequently assessed by different haemodynamic variables that could be targeted as the endpoints for fluid therapy and resuscitation. Fluid balance is the crucial factor in the maintenance of haemodynamic stability, tissue oxygenation and organ function. When the haemodynamic monitoring is applied in a rigorous and consistent manner, it reduces mortality and length of stay as well as costs incurred. There are a number of tests which describe the effectiveness of the invasive haemodynamic monitoring procedures usage. Since the pulmonary artery catheter (PAC) had been introduced into clinical practice it was considered as a golden standard for cardiac output measurements, haemodynamic and fluid balance assessment. Nevertheless, in previous 10 years new minimally invasive and noninvasive simple techniques for haemodynamic monitoring and patient's hydroelectricity status evaluation have been developed. They can replace PAC under different clinical circumstances and some of these techniques

[A look into the larynx--two centuries along the path of laryngoscopy]

Both the design and purpose of the laryngoscope have been changed significantly since Alfred Kirstein invented his own "laryngeal mirror"--the autoscope. An initially straight, rigid oesophageal tube has been reshaped into a number of laryngeal blade modifications, suitable for use in various patient subpopulations. A tool initially intended to help otorhynolaryngologists diagnose and treat laryngeal diseases has been transformed into an instrument intended to help anesthesiologists intubate the trachea for the purpose of either anesthesia administration or airway maintenance. As direct laryngoscopy depends greatly upon individual manual skills, there has been almost no beginner who feels no proud of his first successful intubation. Thus, we should never forget the pioneers of laryngoscopy whose curiosity, creativity, and enthusiasm enabled us to give a clear and safe look into the larynx.

Simultaneous surgical treatment of ruptured abdominal aortic aneurysm and acute carotid occlusive disease

Combined rupture of abdominal aortic aneurysm and acute thrombosis of internal carotid artery is extremely rare but fatal combination resulting in high mortality rate. Presented case, shows successfully performed simultaneous surgery of ruptured abdominal aortic aneurysm and acute cerebrovascular insult caused by thrombosis of carotid artery in 81 year-old male. Post operative course was uneventfull. At 24 months follow up patient was in good condition, with full neurological recovery. Simultaneous surgical treatment of acute occlusive carotid disease and ruptured abdominal aortic aneurysm (RAAA) seems to be the only life saving procedure for this rare, but very complicated condition. To our knowledge, this is the first reported successful simultaneous surgical treatment of RAAA and acute thrombosis of internal carotid artery.

New organic chemistry of sulfur dioxide

Simple 1,3-dienes undergo highly stereoselective hetero-Diels-Alder additions with SO2 at low temperature giving sultines. These reactions that are faster than the more exothermic cheletropic additions of SO2-producing sulfolenes. This has led to the invention of a new C-C bond-forming reaction combining electron-rich dienes and alkenes with SO2. The reaction cascade has been exploited to develop combinatorial, one-pot, four-component syntheses of polyfunctional sulfones, sulfonamides, and sulfonic esters. It also allows us to generate, in one-pot operations, enantiomerically enriched polypropionate fragments containing up to three contiguous stereogenic centers and a (E)-alkene unit. These fragments can be used directly in further C-C bond-forming reactions, such as cross-aldol condensations, thus permitting the expeditious construction of complicated natural products of biological interest (e.g., Baconipyrones, Rifamycin S, Apoptolidinone) and analogues. New ene reactions of SO2 have also been discovered; they open new avenues to organic synthesis.

Mechanism of the diphenyldisulfone-catalyzed isomerization of alkenes. Origin of the chemoselectivity: experimental and quantum chemistry studies

Polysulfone- and diphenyldisulfone-catalyzed alkene isomerizations are much faster for 2-alkyl-1-alkenes than for linear, terminal alkenes. The mechanism of these reactions has been investigated experimentally for the isomerization of methylidenecyclopentane into 1-methylcyclopentene, and theoretically [CCSD(T)/6-311++G(d,p)//B3LYP/6-311++G(d,p) calculations] for the reactions of propene and 2-methylpropene with a methanesulfonyl radical, MeSO2*. On heating, polysulfones and (PhSO2)2 equilibrate with sulfonyl radicals, RSO2*. The latter abstract allylic hydrogen atoms in one-step processes giving allylic radical/RSO2H pairs that recombine within the solvent cage producing the corresponding isomerized alkene and RSO2*. The sulfinic acid, RSO2H, can diffuse out from the solvent cage (H/D exchange with MeOD,D2O) and reduce an allyl radical. Calculations did not support other possible mechanisms such as hydrogen exchange between alkenes, electron transfer, or addition/elimination process. Kinetic deuterium isotopic effects measured for the (PhSO2)2-catalyzed isomerization of methylidenecyclopentane and deuterated analogues and calculated for the H abstraction from 2-methylpropene and deuterated analogues by CH3SO2* are consistent also with the one-step hydrogen transfer mechanism. The high chemoselectivity for this reaction is not governed by an exothermicity difference but by a difference in ionization energies of the alkenes. Calculations for CH3SO2* + propene and CH3SO2* + 2-methylpropene show a charge transfer of 0.34 and 0.38 electron, respectively, from the alkenes to the sulfonyl radical in the transition states of these hydrogen abstractions.

A biased Gm haplotype and Gm paraprotein allotype in multiple myeloma suggests a role for the Gm system in myeloma development

The association between a particular Gm haplotype and susceptibility to multiple myeloma (MM) is not clear. The reason is probably because no investigations have so far been carried out on the relationship between the Gm haplotype, which represents the inherited combination of IgG Gm allotypes, and the Gm allotype expressed at the IgG paraprotein (M-component), which reflects the enhanced gene expression within the haplotype in MM. We studied the incidence of Gm allotypic markers present in IgG subclasses in the serum from 52 patients with MM and in parallel with the isolated IgG paraproteins. The results showed that 84.6% of the patients were heterozygous for haplotypes Gm(a; z; n-; g;)/Gm(f; n+/n-; b1; b0; b5) and 15.3% were homozygous for Gm(f; n/n-; b1; b0; b5), while no homozygous Gm(a; z; n-; g) individuals were found among the studied patients. The incidence of these combinations in the healthy population in Serbia is 34%, 66% and < 1%, respectively. Subjects with Gm(a; z; n-; g)/Gm(f; n+/n-; b1; b0; b5) combination are over 10 times [odds ratio (OR) = 10.69; 95% confidence interval 1.67-68] as likely to be affected by the disease as the subjects with homozygous Gm(f; n+/n-; b1; b0; b5) combination (OR = 0.35, 95% confidence interval 0.06-2.23). However, despite the Gm heterozygosity, most of the Gm(a; z; n-; g;)/Gm(f; n+/n-; b1; b0; b5) positive patients with MM (86.3%) had IgG paraprotein with the allotypic marker from the Gm(f; n+/n-; b1; b0; b5) haplotype. Together with patients homozygous for this haplotype, the relative number of patients with serum IgG paraprotein carrying allotypic marker from the Gm(f; n/n-; b1; b0; b5) haplotype was 88.5%. These results suggest that the development of an M-component could be related to a disturbance on chromosome 14q32 carrying the Gm (f; n+/n-; b1; b0; b5) set of genes.

[Perspective of mechanical ventilation of lungs]

Mechanical ventilation of lungs during the long history has gone through different phases, which have been associated with technological and scientific development of its time. This is the most complex process and in spite of many progress it does not solve all problems, maintained of respiratory homeostasis, especially in patients with difficult lungs damage. Therefore, there is an existing need for further development of mechanical ventilation of lungs. Over the past time, a number of innovative approaches or adjuncts to mechanical ventilation have been actively researched. Many of these have shown some promise in improving our ability to provide ventilatory support. Which of these innovations will outlast the future? Based on actual development at innovations of mechanical ventilation, it can be assumed that it will be: protective lung ventilation, special form of gas exchange, weaning from mechanical ventilation, noninvasive and home use ventilators, development in fallowing patient's condition and pharmacotherapy development.

Hydrothermal synthesis and nanostructure of carbonated calcium hydroxyapatite

The influence of precursor concentration, pressure, temperature and time of hydrothermal synthesis on the development of calcium hydroxyapatite structure has been analyzed. The obtained results show that it is possible to adjust the conditions of hydrothermal synthesis from solutions of relatively high concentrations to obtain calcium hydroxyapatite nanopowders of well-defined structure. The relationship between the synthesis and the lattice parameters, as well as the crystallite size and the microstructure of synthesized hydroxyapatite has been established. The synthesized powders are preferentially carbonated hydroxyapatite of the B type in the form of agglomerates that accommodate two-modal size pores of 1.5-10 and 50-200 nm. The structure of calcium hydroxyapatite particles consists of crystallites 8-22 nm in size, bound within prime particles, which size is between 10 and 63 nm, that in turn form bigger agglomerates 200 nm in size, which further cluster building up agglomerates 5-20 microm in size.

Allyl, Methallyl, Prenyl, and Methylprenyl Ethers as Protected Alcohols: Their Selective Cleavage with Diphenyldisulfone under Neutral Conditions

Diphenyldisulfone is a mild and efficient reagent for selective cleavage of methylprenyl (2,3-dimethylbut-2-en-1-yl), prenyl (3-methylbut-2-en1-yl), and methallyl (2-methylallyl) ethers. These reaction conditions are compatible with the presence of other protecting groups such as acetals, acetates, and allyl, benzyl, and TBDMS ethers. Exposure of 2,3-dimethylbut-2-en-1-yl and 3-methylbut-2-en1-yl ethers to diphenyldisulfone led to the formation of 2,3-dimethylbuta-1,3-diene and isoprene, respectively. 2-Methylallyl ethers undergo isomerization to 2-methylpropenyl ethers, which are easily hydrolyzed into the corresponding free alcohols and isobutyraldehyde. [reaction: see text]

The role of nitric oxide in treatment of acute lung injury after surgery with extracorporeal circulation

Postoperative acute lung injury (ALI) compromises oxygen transfer across alveolar-capillary membrane with consecutive hypoxia, one of its indicators being reduction of oxygenation index PaO2/FiO2 below 40 kPa (300 mm Hg). Management of ALI includes different procedures like mechanical lung ventilation (MLV), drugs and others. One of the new possibilities for treatment of ALI is nitric oxide (NO) inhalation. The aim of this prospective study was to examine the role of NO inhalation in treatment of ALI. 14 patients with ALI developed immediately after operation with extracorporeal circulation (ECC) were included in the study. Group A (n = 8) inhaled NO and group B (n = 6) did not inhale NO during treatment of ALI. All other therapeutic measures were the same in both groups. The groups were similar in relation to demographic data, type of surgery and duration of ECC. PaO2/FiO2 was calculated before operation (T1), immediately after surgery (T2) and after lung recovery, when the need for MLV stopped (T3). The duration of MLV was also registered. PaO2/FiO2 (kPa) in referent times was in group A 54,9 ? 1,6, 33,8 ? 1,2 and 46,2 ? 0,8 and in group B 52,2 ? 1,1, 33,5 ? 1,5 and 47,3 ? 0,9, respectively. There was a statistically significant decrease of PaO2/FiO2 in T2 and T3 vs T1 in both groups (p < 0,05), while the difference between the groups was not statistically significant. The duration of MLV (h) in group B (28,5 ? 1,6) was statistically significantly shorter than in group A (63,1 ? 8,7) (p < 0,01). According to the results of this study we conclude that NO inhalation during ALI after surgery with ECC significantly reduces the duration of MVL and improves pulmonary recovery .

A simple and rapid analysis of triplet repeat diseases by expand long PCR

It is now known that 15 monogenic, mostly neurological, disorders are caused by the same type of mutations that occur in trinucleotide repeat sequences in certain genes. Since they share a nonspecific and variable phenotype, the accurate diagnosis could be made only by DNA analysis. We developed an Expand Long PCR assay that provides more reliable molecular diagnosis of such disorders. Its main characteristics are robust amplification of expanded alleles, simplicity, low cost and speed. We suggest the use of Expand Long PCR for routine molecular diagnosis of triplet repeat diseases, and present such analysis of the fragile X syndrome, myotonic dystrophy and Huntington's disease.

[Periapical surgery of the molars]

INTRODUCTION

If loss of a great number of teeth occurs, one molar in the lateral segment is of great importance. Contemporary techniques and materials provide extremely successful conservative treatment of pulpal diseases and apical periodontitis. In some cases, however, surgery is indicated.

INDICATIONS

Indications for periapical surgery used to be a matter of double standards. If periapical surgery is indicated in incisors, it is performed without delay, but if it is indicated in molars, it is often exchanged for extraction. Surgical access in the region of upper and lower molars is specific in regard to much more frequently operated incisors due to anatomic structures at the surgical site. Canal filling techniques, implants, endodontic surgical procedures are of importance and can provide better healing. High quality canal filling is condition sine qua non in treatment of apical periodontitis. It is performed prior surgery, by conventional orthograde endodontic techniques, during surgery by orthograde technique and/or retrogradely. Implants provide better bone healing and are recommended in surgery of molar apex. Surgical packing has numerous advantages (better psychological and mechanical care).

CONCLUSION

Good knowledge of anatomy and surgical techniques is a pre-requisite for molar apicoectomy. Careful establishment of indications and good relations with the patient provide good prognosis of this therapeutic method.

[Specifics of mastication with complete dentures]

INTRODUCTION

Mastication is a process characterized by alternating phases of physiological inactivity, food intake, initial food crumbling, mouthful formation and deglutition. Although there is a so called human type of mastication, this process is individual for variety of reasons. Mastication is not an innate characteristic and it must be learned, but once it is learned, it gets a reflexive function, demanding maximal involvement of the highest nervous system centers.

DISCUSSION

Specificities of mastication in complete denture wearers are caused by specificities connected to changes of the oral cavity due to teeth loss, technical features of complete dentures and quality of their manufacture. Loss of teeth causes loss of periodontal receptors consequently damaging the source of information which, as long as teeth are present, travels from the oral cavity towards the central nervous system and regulates the masticatory muscles activity. As one of the consequences of periodontal receptors' loss, interocclusal perception decreases, because the number of receptors within the masticatory mucosa is negligible. Another problem is that loss of teeth causes loss of the occlusal surface. Occlusal surface is considered to be the only reference coordinate of the zero intermaxillary separation with precise spatial representation within the someostatic field cortex. Permanent loss of antagonistic contact causes disappearance of the memory pattern of the occlusal surface. Therefore completely edentulous mouths are characterized by disintegration of the free interocclusal space. Masticatory forces' value directly depends on the: size of muscles creating the forces, their position in the mandibula, shape of the edentulous alveolar ridge, type of chewing, the relationship between the height of the branch, length of the mandibular body, gonial angle, mandibular angle in relation to the anterior cranial base and posterior facial height and the degree of intermaxillary separation. Bite forces in complete denture wearers are significantly decreased in relation to persons with natural teeth. There is a fundamental difference in the distribution of the functional energy in complete denture wearers and subjects with intact teeth. Persons with natural teeth tend to generate energy through bolus, whereas in complete denture wearers most of the chewing energy is distributed outside bolus, directly through the denture base on the supporting tissues.

RESULTS

As the result of this specific dynamics stress of supporting tissues often occurs with consequential mucosal inflammation and rapid alveolar bone resorption. Reduction of masticatory efficacy in denture wearers may be caused by irregular activity of masticatory musculature or is the consequence of irregular flow of energy during mastication. In comparison with young examinees with healthy teeth, authors have registered that complete denture wearers need about seven times more masticatory movements to achieve equal number of sample parts.

CONCLUSION

It has been documented by experience and also scientifically proved, that the satisfaction of complete denture wearers is not often proportional with objective functional denture values. Comparison of subjective parameters with objective test results reveals that the percentage of complete denture wearers who consider their dentures to be good, although they objectively are not such, is significantly higher than the percentage of those who complain about their dentures, although they are functionally proper. Our study comprised patients (average age of 69) who wore complete dentures longer than five years.

[Current knowledge on resorption of the edentulous alveolar ridge]

INTRODUCTION

Due to inside physiological processes of the bone tissue of the residual ridge, the above is identical with the bone tissue in other parts of the body. All bones which contain a larger percentage of substance spongiosa are very sensitive to the changes in remodelation. In mandibula the arrangement of the bone trabeculas is in the same direction with the spongious bone traectoria. In maxillae, functional demands for transmitting the forces, are fulfilled by a larger number of trabeculas per square unit. The atrophia of the residual ridge was a result of teeth loss, which means that there was no working tension on the bone, affected by the periodontal ligament in a physiological way.

MATERIAL AND METHODS

The resent knowledge of the above problems indicates that inflammation and pressure which develop under the mobile denture cause an intensive process of resorption of edentulous arch. In periodontitis the connection between lymphocytes and other inflammatory cells on one side, and the residual bone resorption level on the other side, were proved by stereometrical methods. The ELISA method proved that cytokine interleukin-1 beta (IL-1 beta), IL-1 beta and the tumor necrosis factor alpha, were the major factors in the stimulation of bone resorption, and inhibitatory of the above, as well. Mononucleous blood cells under the influence of the Porphyromonas gingivalis were forming interleukin-1 which explains that the etiology of bone resorption can be affected by the infection, too.

DISCUSSION

It has been proved that there is a direct relation between the pressure under the mobile denture and the residual ridge resorption level on the other side. It seems that the frontal areas of the edentulous are more susceptible to resorption. It is considered that the orthopantomography is the most acceptable method in level measuring of the reduction of residual ridge. The advantages of the above method are simplicity, precision, repeating possibilities, and comparation of the radiographs in time interval which makes it possible to control the development of changes. Densitometric measuring of osteoporotic changes is also possible, due to above method.

CONCLUSION

The scientific contribution to research and prevention of negative consequences of the residual ridge resorption is the most valuable. Tere were many possibilities in using the indirect physiological role of piezoelectric field on the osteoclasts and activation by the AKMA. The effect of the fluor in drinking water as the element which has preventive role in reduction of the residual ridge, has been established. Due to the fact that the occlusal pressure which transmits itself through the mobile denture has an important role in resorption of the residual ridge, acts of terciare prevention include application of soft acrylates and reduction of occlusal surface.