Unique Ring Research Articles

Total Synthesis of Lettucenin A, a Guaianolid Phytoalexin from Lactuca sativa var. capitata

Abstract Lettucenin A, a novel composite phytoalexin with 2H-cyclohepta[b]furan-2-one ring system was synthesized from an indanone. The unique ring system was constructed by reductive ring expansion of a dibromomethylcyclohexadienone.

A novel bicomponent hemolysin from Bacillus cereus

A procedure combining isoelectric focusing (Sephadex IEF) and fast protein liquid chromatography (Superose 12; Mono-Q) removed hemolytic activity (presumably a contaminant) from partially purified preparations of the multicomponent diarrheal enterotoxin produced by Bacillus cereus. However, when the separated fractions were recombined, hemolytic activity was restored, suggesting that hemolysis is a property of the enterotoxin components. Combined fractions exhibited a unique ring pattern in gel diffusion assays in blood agar. During diffusion of the hemolysin from an agar well, the erythrocytes closest to the well were not lysed initially. After diffusion, hemolysis was observed as a sharp ring beginning several millimeters away from the edge of the well. With time the cells closer to the well were also lysed. This novel hemolysin consists of a protein (component B) which binds to or alters cells, allowing subsequent lysis by a second protein (component L). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis, isoelectric focusing, and Western blot analysis showed that hemolysin BL has properties similar to those described previously for the enterotoxin and that both components are distinct from cereolysin and cereolysin AB.

Ascidiatrienolids A-C, novel lactonized eicosanoids from the colonial marine ascidian Didemnum candidum

Three new eicosanoids ( 1-3) possessing a unique 9-membered ring lactone and novel sites of oxidation have been isolated from the colonial marine ascidian Didemnum candidum (F. Didemnidae). These compounds further illustrate some intriguing differences in the pathways of eicosanoid production between mammals and several marine invertebrates.

Myrocin C, a new diterpene antitumor antibiotic from Myrothecium verrucaria. II. Physico-chemical properties and structure determination.

The structure of a new antitumor antibiotic, myrocin C, from a strain of Myrothecium verrucaria was characterized as a pentacyclic pimarane diterpene composed of a gamma-lactol group and a unique cyclopropane ring on the basis of its physico-chemical properties and spectroscopic data as well as a single-crystal X-ray diffraction analysis of its monoacetyl derivative.

Unique factorisation of normal elements in non-commutative rings

In the literature there are several generalisations to non-commutative rings of the notion of a unique factorisation domain from commutative algebra. This paper follows in the spirit of [1, 3] and is set in the context of Noetherian rings. In [3], A. W. Chatters and the author denned a Noetherian UFR (unique factorisation ring) to be a prime Noetherian ring R in which every non-zero prime ideal contains a prime ideal generated by a non-zero normal element p, that is, by an element p such that pR = Rp. The class of Noetherian UFRs includes the Noetherian UFDs studied by Chatters in [1], while a commutative Noetherian ring is a UFR if and only if it is a UFD in the usual sense. For a Noetherian UFR R, the following are simple consequences of the definition:(i) every non-zero ideal of R contains a non-zero normal element;(ii) the set N(R) of non-zero normal elements of R is a unique factorisation monoid in the sense of [4, Chapter 3].

Regularity of trace rings of generic matrices

is called the ring of m generic n x n matrices G,, n. The F-subalgebra of M,,(em,,) generated by G,,. and Tr(G,,.) is the ring of m generic n x n matrices and is denoted by T,, n. These trace rings appear naturally in the study of finite dimensional representations of free algebras and in the invariant theory of n x n matrices, [7]. Unlike rings of generic matrices, T,, n shares some properties with commutative polynomial rings; e.g., they are maximal orders and even unique factorization rings in the sense of Chatters and Jordan. However, their homological properties are far from being understood. The main aim of this paper is to prove the following result.

Total Synthesis of (±)-Furodysin and (±)-Furodysinin

Abstract Furodysin and furodysinin, marine origin furanosesquiterpenes having a unique carbocyclic ring system, have been first synthesized as racemic forms from a cis-decalone derivative.

Biosynthesis of 2'-deoxycoformycin: evidence for ring expansion of the adenine moiety of adenosine to a tetrahydroimidazo[4,5-d][1,3]diazepine system.

2'-Deoxycoformycin (2'-dCF), a nucleoside antitumor agent produced in trace quantities by Streptomyces antibioticus, has been shown in earlier work to originate from the intact carbon-nitrogen framework of adenosine. Additional experiments using 13C and two-dimensional Fourier transform NMR techniques, together with radiolabeling studies, identify the C-1 of D-ribose, and not the tetrahydrofolate "C-1 pool", as the source of the C-7 carbon in the aglycon of 2'-dCF. These results show that the adenine portion of adenosine (or a nucleotide thereof) undergoes a unique ring expansion, by insertion of a -CH2- unit between the N-1 and C-6 of the adenine ring, to furnish the 1,3-diazepine portion of 2'-dCF.

Design and synthesis of bioactive cyclic peptides, AM-toxin I and gramicidin S

In order to investigate the structure-activity relationship of phytotoxic AM-toxin I and antibiotic gramicidin S, various analogues were synthesized and used for conformational analysis and bioassay. Circular dichroism and NMR studies of AM-toxin compounds showed that a unique and rigid ring conformation of AM-toxin I is required for the specific activity. From the circular dichroism studies and antimicrobial assays of gramicidin S compounds, a region of type IF β-bend in gramicidin S was found to be important for the maintenance of the potent conformation. These results show the possibility of the conscious introduction of activity by design by modification of AM-toxin I and gramicidin S.

CV-1, a new antibiotic produced by a strain of Streptomyces sp. II. structure determination.

The structure of a new antibiotic, CV-1 was determined to be 1,2-diamino-1,2-N,N'-carbonyl-1,2-dideoxy-alpha-D-glucose hydrate by spectral and chemical studies. CV-1 possessed a unique open ring hemiaminal structure. CV-1 synthesized from N-carbamoyl-D-glucosamine was identical to material isolated from fermentation.

Non-Commutative Unique Factorisation Rings

Journal of the London Mathematical SocietyVolume s2-33, Issue 1 p. 22-32 Notes and papers Non-Commutative Unique Factorisation Rings A. W. Chatters, A. W. Chatters School of Mathematics, University of Bristol, University Walk, Bristol BS8 1TNSearch for more papers by this authorD. A. Jordan, D. A. Jordan Department of Pure Mathematics, University of Sheffield, Hounsfield Road, Sheffield S3 7RHSearch for more papers by this author A. W. Chatters, A. W. Chatters School of Mathematics, University of Bristol, University Walk, Bristol BS8 1TNSearch for more papers by this authorD. A. Jordan, D. A. Jordan Department of Pure Mathematics, University of Sheffield, Hounsfield Road, Sheffield S3 7RHSearch for more papers by this author First published: February 1986 https://doi.org/10.1112/jlms/s2-33.1.22Citations: 39AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volumes2-33, Issue1February 1986Pages 22-32 RelatedInformation

Trace rings of generic matrices are unique factorization domains

A. W. Chatters and D. A. Jordan defined in [0] a unique factorization ring to be a prime ring in which every height one prime ideal is principal. In this note we will prove that the trace ring of m generic n × n-matrices satisfies this condition.Throughout this note, k will be a field of characteristic zero. Consider the polynomial ring S = k[;1≤i, j≤n, 1≤l≤m] and the n × n matrices Xl = in Mn(S). The k-subalgebra of Mn(S) generated by {Xl; 1≤l≤m} is called the ring of m generic n × n matrices Gm,n. Adjoining to it the traces of all its elements we obtain the trace ring of m n × n generic matrices, cfr. e.g. [1].

Addition of hydrogen halides to isolongifolene : formation of novel sterically-diverted bicyclic monoolefinic primary halides

When the tricyclic isolongifolene 2 is exposed to HX(HBr, HI) in AcOH, a unique ring fragmentation takes place resulting in the formation of a novel bicyclic monoolefinic primary halide 9 / 10 . The closely related tetracyclic cyclopropane isomer 14 of the tricyclic olefin 2 , on reaction with HI in AcOH, also affords 10 . Attempted solvolysis of 9 with AgClO 4 in 50% aqueous acetone generates essentially isolongifolene 2 . These results can be best interpreted mechanistically in terms of a nonclassical carbocation 21 . The bicyclic primary acetate 11 resulting from action of KOAc-DMF on 9 / 10 , on hydrolysis with base gives the primary alcohol 12 which has been converted to the acid 13 by oxidation with Jones reagent.

Cmr Assignments of the Securinine Alkaloids

The cmr spectrum of securinine (11, allosecurinine (2), and their boro- hydride reduction products (3 and 4) have been assigned on the basis of lanthanide shift experi- ments and specific deuteration. The securinine alkaloids comprise a group of about a dozen alkaloids sharing a unique ring structure and biosynthesis (1,2). It has recently been demonstrated that securinine is a stereospecific GABA, receptor antagonist of restricted conformation (3), making it a useful tool for understanding GABA receptor topography. It was therefore of interest to assign the cmr spectra in this series in order to facilitate identification of new alkaloids and to understand better the limited conformational mobility of the alkaloids. Single-frequency off-resonance decoupling (SFORD) experiments were of limited utility in assigning resonances because the respective methylene, methine, and quater- nary carbon resonances occurred in closely spaced groups that could not be completely assigned without further experimental techniques. The lanthanide shift reagent Eu(fod), provided invaluable information, and the trends in chemical shifts throughout the series were correlated with conformation predicted by MM2 molecular mechanics calculations. Specific deuteration was helpful in assigning the resonances of dihy- drosecurinine (3). Finally, the previously assigned spectrum of indolizidine (4) pro- vided confirmation. Assignments are tabulated in Table 1 for securinine (l), al- losecurinine (2), 14,15-dihydrosecurinine (3), and 14,15-dihydroallosecurinine (4): Detailed comparisons ofpredicted and observed shifts are not presented for all cases, be- cause a simple graphical comparison of the induced shifts of each set of two or three am- biguous resonances gave identical asignments. The distance term (r3) in the McCon- nell-Robertson equation (5,7) is dominant over the angle term (cos 2 8) for the sec- urinine alkaloid structures.

Total Synthesis of Antibiotic A23187 (Calcimycin) from D-Glucose: Communication

Abstract Antibiotic A23187 1 is a cation ionophore highly specific for Ca2+. Because of its unique dioxaspiro ring structure as well as its biological activities,2 several synthetic approaches to the compound have been reported.3 We report here the first example of the total synthesis of based on the use of a carbohydrate template.4 The target structure was synthesized from the chiral synthons or “chirons”5 and via a key intermediate , as shown in Scheme I. A thermodynamically controlled, acid catalyzed ring closure of was expected to provide a correct configuration at the spiro center C-14 according to the anomeric effect.6 The two chirons and were prepared from -glucose via the same intermediate -as follows (Scheme II).

A generalization of Torres’ second relation

Let $L = {K_1} \cup \cdots \cup {K_\mu }$ be a tame link in ${S^3}$ of $\mu \geqslant 2$ components, and let ${L_\mu }$ be its sublink ${L_\mu } = L - {K_\mu }$. Let $H$ and ${H_\mu }$ be the abelianizations of ${\pi _1}({S^3} - L)$ and ${\pi _1}({S^3} - {L_\mu })$, respectively, and let ${t_1}, \ldots ,{t_\mu }$ (resp., ${t_1}, \ldots ,{t_{\mu - 1}}$) be the usual generators of $H$ (resp., ${H_\mu }$). If $\phi :{\mathbf {Z}}H \to {\mathbf {Z}}{H_\mu }$ is the (unique) ring homomorphism with $\phi ({t_i}) = {t_i}$ for $1 \leqslant i < \mu$, and $\phi ({t_\mu }) = 1$, then Torres’ second relation is equivalent to the statement that $\phi {E_1}(L) = (({\prod _{i < \mu }}t_i^{{l_i}}) - 1) \cdot {E_1}({L_\mu })$, where for $1 \leqslant i < \mu$, ${l_i}$ is the linking number ${l_i} = l({K_i}, {K_\mu })$. We prove that if $I{H_\mu }$ is the augmentation ideal of ${\mathbf {Z}}{H_\mu }$, then for any $k \geqslant 2$, \[ {E_{k - 1}}({L_\mu }) + \left ( {\left ( {\prod \limits _{i < \mu } {t_i^{{l_i}}} } \right ) - 1} \right )\cdot {E_k}({L_\mu }) \subseteq \phi {E_k}(L) \subseteq {E_{k - 1}}({L_\mu }) + I{H_\mu }\cdot {E_k}({L_\mu })\] and examples are given to indicate that either of these inclusions may be an equality. This theorem is used to generalize certain known properties of ${E_1}$ to the higher ideals.

Inhibition of nuclear uptake and ATP-Sepharose binding of progesterone-receptor complex by aurintricarboxylic acid

Aurintricarboxylic acid (ATA) was used as a low-molecular-weight chemical probe for the analysis of nuclear binding site(s) of avian progesterone receptor. The cytosol from the oviducts of white Leghorn hens or diethylstilbestrol-primed immature chicks was fractionated with (NH 4) 2SO 4, redissolved and labeled with 3H-labeled R5020 for 2 h at 4 °C. An incubation with 0.1–0.5 m m ATA at 4 °C completely blocked the uptake of progesterone-receptor complex by isolated hen oviduct nuclei. The steroid binding properties of the receptor and the sedimentation characteristics of the progesterone-receptor complex appeared to remain intact under these conditions. The commercially available as well as laboratory-synthesized ATA has been known to be a mixture of several compounds. Eight different components of ATA were separated on silica gel (Kontes) by thin-layer chromatography using a solvent system containing chloroform, formic acid, and acetone (100/5/15, v v ). The components were named according to their migration spot on the silica plates, 8 being the slowest and 1 being the fastest. Components 4–8 blocked the nuclear uptake by 40–70% at 0.1 m m whereas at higher concentration (1.0 m m) Components 7–8 completely inactivated the progesterone-receptor complex; Components 5–6 also blocked the nuclear uptake significantly. The effects of ATA appeared to be irreversible; dialysis of ATA-treated preparations, or an addition of divalent cations, BSA, or ATP did not remove its inhibitory influence. Further analysis on several compounds structurally related to ATA revealed that the unique aurintriphenylmethane ring system and the carboxylic acid groups are both necessary for its inhibitory effects on progesterone receptor.

NMR Spin-Lattice Relaxation Time Determination of the Barriers to Ring Rotation in SOlid bid-Cyclopentadienyl Molybdenum Dichloride

Abstract The potential energy barriers to rotation of the cyclopentadienyl rings in bis-cyclopentadienyl molybdenum dichloride have been measured by spin-lattice relaxatio time methods. The barrier depends upon the local environment of the ring and values of 12.76,8.64. 8.64, and 1.47 kJ mol−1 were obtained for the four crystallographically unique cyclopetadienyl rings of the two molecules in the asymmetric unit.

単原子ペリ架橋ナフタレン類の化学

Single-atom peri-bridged naphthalenes are compounds in which the 1-and 8-carbon atoms of a naphthalene ring are bonded to a single atom in a bridging group (Z), forming a four-membered ring. The present review is concerned with the synthesis, structure, and reaction of this highly-strained unique ring system.

Synthetic strategies to the ergoline ring system of ergot alkaloids

The synthetic strategies to the ergoline ring system (I) have been outlined, and discussed in terms of their yields and limitations. The total syntheses of ergoline, racemic and natural dihydrolysergic acid, lysergic acid, isosetoclavine, penniclavine, elymoclavine and chanoclavine-I have been described. These illustrate the synthetic problems that have been encountered in ergoline chemistry. The role of key intermediates has been emphasised. Modification to the original schemes have not given yields or procedures that can compete with the production by fermentation of ergot alkaloids. However, it is hoped that the synthetic strategies discussed in this article will provide useful information, when considering new approaches, or modification, to the unique heterocyclic ring system of ergoline.