Parent Ring Research Articles

4H-thieno[3,4-c]pyrrole: synthesis and characterization of the parent ring system

4H-Thieno[3,4-c]pyrrole (4) was synthesised from the azide (8) by intramolecular 1,3-dipolar cycloaddition followed by acid-catalysed 1,3-dipolar cycloreversion of the dihydrotriazole intermediate (9); the crystal structure of one of the products formed on trapping (4) with N-phenylmaleimide has been determined.

ChemInform Abstract: 2H‐Pyrrolo(3,4‐b)pyridine and 2H‐Pyrrolo(3,4‐c)pyridine: Synthesis of the Parent Ring System and the Diels‐Alder Reaction.

Abstract3‐Di(ethoxycarbonyl)ethylidene‐2‐methylpyridine (I) is converted to the azide (IV) which undergoes intramolecular 1,3‐dipolar cycloaddition, forming the triazoline (V).

2H-Pyrrolo[3,4-b]pyridine and 2H-pyrrolo[3,4-c]pyridine: synthesis of the parent ring system and the Diels-Alder reaction

2H-Pyrrolo[3,4-b]pyridine (1) and 2H-pyrrolo[3,4-c]pyridine (2) were prepared and reacted with N-phenylmaleimide to give Diels-Alder adducts.

Nitrile sulphides. Part 7. Synthesis of [1]benzopyrano[4,3-c]isothiazoles and isothiazolo[4,3-c]quinolines

O-Hydroxybenzonitrile sulphide (1a), generated by thermal decarboxylation of the corresponding 1,3,4-oxathiazol-2-one, reacts with dimethyl acetylenedicarboxylate to afford methyl 4-oxo-4H-[1]benzopyrano[4,3-c]isothiazole-3-carboxylate (6a), from which the parent ring system (6c) can be prepared by hydrolysis and decarboxylation. The same products are formed from the acetoxy analogue (1b)via hydrolysis of isothiazole (5b). O-Acetamidobenzonitrile sulphide (1c) reacts similarly forming isothiazole (5c) and subsequently isothiazolo[4,3-c]quinolin-4(5H)-one (7c) by hydrolysis, ring closure, and decarboxylation. Cycloadditions to ethyl cyanoformate, ethyl propiolate, and diethyl fumarate have also been examined.

Novel heterocyclic intermediates for new dyes and pigments

The synthesis of two new heterocyclic ring systems of the phenoxazine type is described. These are the 1,4,9-triazaphenoxazine and 1,4,6-triazabenzo[b]phenoxazine. The preparation of the parent ring of 1,4,9-triazaphenoxazine ring system is also reported. Spectroscopic data are in agreement with the assigned structures and the mechanistic pathway to these novel heterocycles is also presented. These ring systems provide a new framework for the development of novel dyes and pigments of the phenoxazine class.

The total synthesis of (±)-petasitolone

The total synthesis of petasitolone (1), a sesquiterpenoid of the eremophilane family, has been accomplished. The key step of this efficient synthesis is the Lewis acid catalyzed Diels–Alder addition of 2-carbomethoxy-2-cyclohexenone (3) to diene 9. The cycloaddition, which gives adduct 16 in good yield, facilitates the rapid construction of the parent ring system of the target molecule and allows an excellent control of the required stereochemistry.

Synthesis of 1,2,3,4‐tetrahydro‐5H‐[1]benzopyrano[3,4‐c]pyridin‐5‐ones. I. 3‐unsubstituted compounds

AbstractSynthesis of 1,2,3,4‐tetrahydro‐5H‐[1]benzopyrano[3,4‐c]pyridin‐5‐ones via a Pechmann condensation of 3‐carbethoxy‐1‐methyl‐4‐piperidone with various phenols is described. The limitations of this method are discussed. Synthesis of the parent ring system 3a via reduction of 1,2,3,4‐tetrahydro‐3‐(phenylmethyl)‐8‐[(1‐phenyl‐1H‐tetrazol‐5‐yl)oxy]‐5H‐[1]benzopyrano[3,4‐c]pyridin‐5‐one (5) is also described.

1H‐pyrazolo[3,4‐d]thieno[2,3‐b]pyridine and its derivatives

AbstractThe synthesis of the parent ring system and some of the derivatives of 1H‐pyrazolo[3,4‐d]thieno[2,3‐b]pyridine are described.

Studies in the heterocyclic series. XX. 1,4‐Diazaphenoxazine and related compounds

AbstractAs part of our program on the synthesis of new psychotropic agents, the parent rings of two diazaphenox‐azines are described. The reaction of 2‐aminophenol and 2,3‐dichloropyrazine in alkaline media gave good yields of 1,4‐diazaphenoxazine. Replacement of 2,3‐dichloropyrazine with 2,3‐dichloroquinoxaline gave on the other hand the heterocycle, 1,4‐diazabenzo[b]phenoxazine. Nitration and S‐oxide formation were achieved by reaction with mixed nitric and sulfuric acids. Mechanistic pathways to these compounds were also discussed.

Electron spin resonance studies of the effects of naturally-occurring excitotoxic amino acid analogues on the physical state of membrane proteins in human erythrocytes

The interaction of the neurotoxic natural products, kainic and ibotenic acids, both of which are also excitatory neurotransmitters and amino acid analogues of glutamic acid, along with the latter compound, with human erythrocyte membranes has been investigated by electron spin resonance methods. Only ibotenic acid caused a statistically significant alteration in the physical state of membrane proteins (P = 0.01) while none of these excitotoxins measurably affected motion of membrane lipids. In order to further investigate some of the molecular characteristics of ibotenic acid that may have contributed to its effect on the conformation of membrane proteins, similar spin labeling studies were performed employing the decarboxylation product and parent ring compound of this excitotoxin, muscimol and isoxazole, respectively. No effect of either of these latter compounds was observed suggesting that the carboxylic acid group of ibotenic acid is essential for its interaction with membrane proteins. These results are discussed in relation to the known different neurotoxic and physiological effects of kainic and ibotenic acids and muscimol.

Heterocycles from substituted amides. IX. 4,5‐dihydro‐1,2,4‐triazin‐6‐(1H)ones from 2‐isocyanoacetates and hydrazine

AbstractThe novel synthesis of 4,5‐dihydro‐1,2,4‐triazin‐6‐(1H)ones, 2, from 2‐isocyanoacetates is described. This synthetic method allows the first synthesis of the unsubstituted parent ring sytem and, in general, gives 2 substituted in only the five position. The assignment of tautomeric structures (2 or 3) to the triazinone products was resolved by spectroscopic means.

Ten-nanometer filaments and mitosis: maintenance of structural continuity in dividing endothelial cells.

By indirect immunofluorescence the behavior of the 10-nm filaments was studied at various stages of mitosis in guinea pig vascular endothelial cells. Interphase cells contain a ring of 10-nm filaments that encircles the nucleus and is maintained in a plane parallel to the substrate. During prophase and metaphase the cells round up and the 10-nm filament ring becomes wavy though still a closed structure. As anaphase progresses the ring then elongates into a rectangle that contains the spindle apparatus and chromosomes. In late telophase, cytokinesis cleaves the 10-nm filaments into crescents at the site of the contractile ring. These crescents then close into rings in the daughter cells. If cytokinesis is inhibited with 5 microgram of cytochalasin B per ml, then cleavage of the 10-nm filaments is blocked and the daughter nuclei remain surrounded by the parent ring. At no point during mitosis does the array of 10-nm filaments undergo major disassembly. These results indicate that, in contrast to the other major cytoplasmic structures, ventral microfilament bundles and cytoplasmic microtubules, which disassemble and reassemble during mitosis, 10-nm filaments remain intact throughout this process. The possibility is discussed that these filaments may function in transport of organelles and structural proteins, and provide the daughter cells with topological information about placement and assembly of these elements within the microtrabecular lattice.

Prolactin release in parent ring doves after brief exposure to their young.

A pigeon crop sac radioreceptor assay was used to measure changes in pituitary prolactin levels in parent ring doves of both sexes on the third day after hatching of their young. After a deprivation of 17 h from the squabs, exposure to a 3-day-old squab for 1 h resulted in a significant decrease in the prolactin content of the pituitary gland as compared with levels obtained in control birds deprived of their young for 18 h. No significant sex differences in prolactin levels were observed in either group. Because exposure to the young also promotes prolactin-induced crop sac growth, it appears probable that the squab-induced decrease in prolactin content of the pituitary gland reflects the release of prolactin into the circulation. Accordingly, the environmental regulation of prolactin secretion in parent ring doves appears similar to that observed in lactating mammals.

SYNTHESIS AND REACTIONS OF SOME 3-SUBSTITUTED S-TRIAZOLO (5,4-B) NAPHTHO (2,1-D) THIAZOLES

Abstract Synthesis of s-Triazolo (5,4-b) Naphtho (2,1-d) thiazolϱ parent ring was recently reported1. The starting material 2-Hydrazino (5,4-b) Naphtho (2,1-d) thiazole (I) was obtained from B Naphthyl amine converting it into thiocyanato, mercapto, chloro and finally 2-hydrazino. In our laboratory we have prepared the same from 2-amino Naphtho (2,1-d) thiazole in a single step in good yields.

Synthesis of furan derivatives. LXXXIV. Kinetic studies of the curtius rearrangement of 5-substituted 2-furoyl azides and related compounds.

Kinetic studies of the thermolytic Curtius rearrangement of set A of 5-substituted 2-furoyl azides (1-6), 5-substituted 2-thenoyl azides (7, 8 and 9) and 2-pyrroyl azide (10), and set B of p-substituted benzoyl azides (11, 12 and 13) and 2-, 3- and 4-pyridinemonocarbonyl azides (14, 15 and 16) in toluene were executed by means of IR (infrared) spectrophotometric method. It was found through the relationship between log k and 1/T that the isokinetic temperature (Q) of the set A and B are Q=371°and 353°K, respectivery. Based on ΔEb and ΔSb, it seems to be reasonable that the reactivity of the each of unsubstituted acyl azides (2, 7, 9 and 12) is very nearly parallel to that the each resonance energy of the parent rings of the above four acyl azides. Additionally, it was found that the substituent dependence on ΔSb in the rearrangement of the 5-substituted 2-furoyl azides (2-6) and also the 5-substituted 2-thenoyl azides (9 and 10) is indifferent to whether the substituents are electron releasing or attracting groups, and on the other hand, the rearrangement of p-substituted benzoyl azides (12 and 13) has ΔSb decreased, respectively.

Chemistry of the phenoxathiins II. Synthesis of 1‐azaphenoxathiin

AbstractThe synthesis of 1‐azaphenoxathiin, the parent ring system of a recently reported class of novel CNS agents is described. The 13C‐nmr spectrum and its assignment are also reported as a model for structure confirmation studies.

ChemInform Abstract: PYRAZOLO(1,5‐A)PYRIMIDINE, SYNTHESIS AND REGIOSPECIFIC ELECTROPHILIC SUBSTITUTION IN THE PYRAZOLE AND/OR PYRIMIDINE RINGS

AbstractDas durch Decarboxylieren der Säure (Ia) bei 170°C erhältliche Pyrimidin (Ib) wird mit 1,1,3,3‐Tetramethoxypropan zu der Titelverbindung (II) kondensiert.

Studies Related to Antitumor Antibiotics. Part III. Syntheses of 1,2,3,4,5,6-Hexahydro-2,3-benzazocin-5-ones as Possible Intermediates in the Biosynthesis of Mitomycins

The synthesis of 8-methoxy-9-methyl-N-p-toluenesulfonyl-1,2,3,4,5,6-hexahydro-2,3-benzazocin-5-one (23) and its conversion via transannular interaction to the 2,3-dihydro-lH-pyrrolo[1,2-a]indole ABC parent ring system of the antitumor antibiotic mitomycin C is described. The possible implication of this result in the biosynthesis of the mitosanes and the connection with the structurally and pharmacologically related pyrrolizidine alkaloids is discussed.

Pyrazolo[1,5-a]Pyrimidine: Synthesis and Regiospecific Electrophilic Substitution in the Pyrazole and/or Pyrimidine Rings

A general cyclization route to pyrazolo[1,5-a]pyrimidines from 3-aminopyrazole and 1,3-dicarbonyl compounds is applied to synthesis of the parent ring system. In nitration of this species the orientation of substitution is strongly reagent dependent. Mixed nitric and sulfuric acids yield the 3-nitro compound, whereas nitric acid in acetic anhydride yields the 6-nitro compound. Brominations yield 3-bromo and 3,6-dibromo species.The majority reacting species in the strongly acidic medium is identified as the 1-protonated entity by conjoint use of approximate molecular orbital calculations and the variation of coupling constant patterns accompanying protonation. The molecular orbital calculations predict successive 3- and 6-substitution by electrophiles in pyrazolo[l,5-a]pyrimidine and its conjugate acid, and an addition–elimination sequence is proposed to account for the observed 6-nitration.

Stereocontrolled synthesis of thestereoisomers of perhydropyrido[2,1,6-de]quinolizine: parent ring system of the coccinellid alkaloids

The two possible perhydropyrido[2,1,6-de]quinolizine stereoisomers were prepared in a stereocontrolled fashion starting from perhydroboraphenalene.