First hypervalent iodine(III)-catalyzed C-N bond forming reaction: catalytic spirocyclization of amides to N-fused spirolactams

A protic solvent, 2,2,2-trifluoroethanol (CF(3)CH(2)OH), was successfully introduced into hypervalent iodine(III)-involved catalytic cycles as an effective solvent, and the first iodoarene-catalyzed intramolecular carbon-nitrogen bond forming reaction was achieved under strong acid-free and mild conditions.     

Universal extra dimensions on real projective plane

We propose a six-dimensional Universal Extra Dimensions (UED) model compactified on a real projective plane RP²${\mathit{RP}}^2$, a two-sphere with its antipodal points being identified. We utilize the Randjbar-Daemi–Salam–Strathdee spontaneous sphere compactification with a monopole configuration of an extra UX₍₁₎$U{(1)}_X$ gauge field that leads to a spontaneous radius stabilization. Unlike the sphere and the S²/Z₂$S^2/Z_2$ orbifold compactifications, the massless UX₍₁₎$U{(1)}_X$ gauge boson is safely projected out. We show how a compactification on a non-orientable manifold results in a chiral four-dimensional gauge theory by utilizing 6D chiral gauge and Yukawa interactions. The resultant Kaluza–Klein mass spectra are distinct from the ordinary UED models compactified on torus. We briefly comment on the anomaly cancellation and also on a possible dark matter candidate in our model.     

Cost-effective production policy for a stochastic unreliable manufacturing system

^** Email: dohi{at}rel.hiroshima-u.ac.jp The paper deals with an economic manufacturing quantity (EMQ)problem for an unreliable manufacturing system in both continuous-and discrete-time settings. The time to machine failure andcorrective and preventive repair times of the production facilityare assumed to follow arbitrary probability distributions. Thetraditional method of determining the EMQ policy for a failure-pronemanufacturing system is based on the minimization of the long-runaverage cost in the steady state. In this paper, an alternativecriterion of optimality called cost effectiveness is introduced.The criteria for the existence and uniqueness of the optimalproduction time maximizing the cost effectiveness are derivedanalytically under general failure and specific repair (correctiveand preventive) time distributions. The optimal cost-effectiveand average cost production policies are numerically calculatedand compared in terms of their performances.     

A new methodology for the synthesis of fluorinated exo-glycals and their time-dependent inhibition of UDP-galactopyranose mutase

Fluorinated carbohydrates constitute a very important class of mechanistic probes for glycosyl-processing enzymes. In this study, we describe the first synthesis of fluorinated and phosphonylated exo-glycals and their corresponding nucleotide sugars in the galactofuranose series. The synthetic protocol that we have developed is a Selectfluor-mediated fluorination/elimination sequence on phosphonylated exo-glycals, and it offers a new entry into fluorinated carbohydrate chemistry. The challenging E/Z stereochemical assignment of the resulting tetrasubstituted alkenes, which bear an alkoxy, an alkyl, a fluoro, and a phosphonyl group, has been achieved through NMR experiments. The corresponding (E)- and (Z)-nucleotide fluorosugars have been prepared and tested as inhibitors of UDP-galactopyranose mutase (UGM). UGM is a flavoenzyme that catalyzes the isomerization of uridine diphosphate(UDP)-galactopyranose into UDP-galactofuranose, a key step of the biosynthesis of important mycobacterial cell-wall glycoconjugates. The two diastereomeric molecules were found to display time-dependent inactivation of UGM, as expected from preliminary results using non-fluorinated exo-glycal nucleotides. The inhibitory properties of the two fluorinated molecules led us to suggest that the inactivation mechanism proceeds through two-electron processes, despite the presence of the flavin cofactor within the UGM catalytic site.     

Halogen-Induced Controllable Cyclizations as Diverse Heterocycle Synthetic Strategy

In organic synthesis, due to their high electrophilicity and leaving group properties, halogens play pivotal roles in the activation and structural derivations of organic compounds. Recently, cyclizations induced by halogen groups that allow the production of diverse targets and the structural reorganization of organic molecules have attracted significant attention from synthetic chemists. Electrophilic halogen atoms activate unsaturated and saturated hydrocarbon moieties by generating halonium intermediates, followed by the attack of carbon-containing, nitrogen-containing, oxygen-containing, and sulfur-containing nucleophiles to give highly functionalized carbocycles and heterocycles. New transformations of halogenated organic molecules that can control the formation and stereoselectivity of the products, according to the difference in the size and number of halogen atoms, have recently been discovered. These unique cyclizations may possibly be used as efficient synthetic strategies with future advances. In this review, innovative reactions controlled by halogen groups are discussed as a new concept in the field of organic synthesis.     

Verification study for an empirical rule in diverse helical conformational behaviors of asymmetric 1,2-diacyl-sn-glycerols in the solution state

Cell-membrane glycerophospholipids and glycolipids have a common asymmetric skeleton of 1,2-diacyl-sn-glycerols. The 1,2-diacyl moiety in solutions permits a rapid equilibrium among three helical conformers, namely gt(+), gg(?), and tg, to display diverse conformational properties. The conformational property changes variably not only by head groups at the sn-3 position, but also by the solvent conditions applied. Recently, we came across an empirical rule in the conformational diversity in the solution state when we assumed the term of ‘helical disparity’ for the equilibrium between gt(+) and gg(?) conformers with reversed helical signs for each other. The sign and magnitude of the helical disparity (%) governs the (+)- or (?)-chirality around the lipid tail and corresponds to the magnitude of the exciton couplet CD (circular dichroism) bands. The empirical rule expresses that the disparity (%) changes linearly by the function of gt(+) population (%). Herein, the rule was verified by ¹H NMR spectroscopy using different types of 1,2-diacyl-sn-glycerols as model compounds. The present paper describes that the rule is formulated with a general equation (Eq-1): ‘helical disparity (%)’?=?[gt(+)?gg(?)] (%)?=?A[gt(+)?B], in which A and B are constants taking values around 1.3 and 38, respectively. This rule is maintained regardless of the 1,2-diacyl and sn-3 substituent groups as far as examined here, while affording several exceptions. With Eq-1 (A?=?1.3, B?=?38), a conformational diagram can be obtained. This allows us to overview the diverse helical conformational properties of the asymmetric 1,2-diacyl-sn-glycerols in the solutions state.