Convergent Access Research Articles

Internetworking VCSEL-Based Hybrid Base Station Towards Simultaneous Wireless and Wired Transport for Converged Access Network

A hybrid base-station (H-BS) scheme that has the potential to establish intercommunications among neighboring access nodes without sending the signals to the edge node to simultaneously transport wireless and wireline services to integrated access nodes is proposed. As the scheme uses vertical-cavity surface-emitting lasers as the light source in the H-BS, it can potentially be realized at low cost without any temperature control.

Unified, Radical-Based Approach for the Synthesis of Spiroketals

[reaction: see text] Functionalization of S-(3-chloro-2-oxo-propyl)-O-ethyl xanthate 1 by two consecutive xanthate transfer reactions, followed by spirocyclization of the resulting dihydroxy ketones, provides a flexible and highly convergent access to diversely substituted spiroketals, containing five-, six-, and seven-membered rings.

Viewpoint: One phone to ring them all

Home basestations turn the threat of convergence and unlicensed wireless access into an opportunity for network operators, says the author.

Synthesis of hindered tertiary amines by a mild reductive amination procedure

An efficient metal-free procedure for the synthesis of tertiary amines by the reductive amination of carbonyl compounds is reported, which allows a convergent access to sterically hindered amines of the general formulas NR(R′) 2 and NRR′R″. The mild and operationally simple protocol uses the Hantzsch ester for transfer hydrogenation and catalytic amounts of thiourea for imine activation.

Radicals from Aldehydes: A Convergent Access to Dienes and δ‐Lactones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

An Expedient, Flexible and Convergent Access to Selectively Protected 1,5‐Dicarbonyl Compounds. Applications to the Synthesis of 2,6‐Disubstituted Pyridines and Thiopyridines.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Total Synthesis of Phosphatidylinositol Mannosides of Mycobacterium tuberculosis.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Radicals from Aldehydes: A Convergent Access to Dienes and δ-Lactones

A convenient method for the generation of O,S-acetal xanthates from aldehydes has been developed. The corresponding nucleophilic radicals undergo facile addition to unactivated olefins and the resulting adducts can be further elaborated to generate dienes and unsaturated δ-lactones.

An Expedient, Flexible and Convergent Access to Selectively Protected 1,5-Dicarbonyl Compounds. Applications to the Synthesis of 2,6-Disubstituted Pyridines and Thiopyridines

Intermolecular addition of 2-oxoalkyl radicals generated from the corresponding S-alkyl-O-ethyl dithiocarbonates on vinyl ketals afforded selectively protected 1,5-dicarbonyl compounds in good yields. These key-intermediates can be converted into a plethora of useful substances. Transformations to pyridines and thiopyridines were given as examples.

Total Synthesis of Phosphatidylinositol Mannosides of Mycobacterium tuberculosis

The total synthesis of phosphatidylinositol mannosides (PIMs), a key class of antigenic glycolipids found on the cell wall of Mycobacterium tuberculosis, is described. The synthetic strategy relied on a [4 + 3] glycosylation of tetramannoside 1 and pseudotrisaccharide 2, which allowed for convergent access to the glycan backbone of the phosphatidylinositol dimannoside (PIM2) and hexamannoside (PIM6). A short practical synthesis of tuberculostearic acid was achieved based on a copper-catalyzed cross-coupling reaction. Union of the glycan and lipid parts resulted in the first total synthesis of native PIM2 and PIM6.

Convergent Access to Ketones, Vinyl Esters and Vinyl Bromides by a Tin‐Free Radical Addition‐Intramolecular Hydrogen Atom Transfer.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Tin‐Free Radical Sequences under Acidic Conditions. Convergent Access to Azole‐Containing Structures.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Convergent access to ketones, vinyl esters and vinyl bromides by a tin-free radical addition-intramolecular hydrogen atom transferDedicated with respect to Professor Gordon Whitham.

Xanthate-mediated intermolecular radical addition, hydrogen atom transfer and sulfonyl radical elimination have been efficiently combined in a new convergent synthesis of ketones and substituted olefins.

Tin-free radical sequences under acidic conditions. Convergent access to azole-containing structures.

[reaction: see text] Various xanthates add efficiently to olefins bearing [1,2,4]triazole, imidazole, or benzimidazole moieties in the presence of camphorsulfonic acid via a radical chain reaction initiated by a small amount of lauroyl peroxide. The adducts may be transformed to more complex molecules by implementing a further radical cyclization.

A novel palladium-mediated coupling approach to 2,3-disubstituted benzo(b)thiophenes and its application to the synthesis of tubulin binding agents.

[structure: see text]. Flexible, convergent access to 2,3-disubstituted benzo[b]thiophenes has been developed. The most concise approach involves sequential coupling of o-bromoiodobenzenes with benzylmercaptan and zinc acetylides to give benzyl o-ethynylphenyl sulfides which react with iodine to give 3-iodobenzo[b]thiophenes in a 5-endo-dig iodocyclization. These iodides can be further elaborated using palladium-mediated coupling and/or metalation techniques. This method has been applied to the synthesis of some novel tubulin binding agents.

Synthesis and Properties of Star-Shaped Multiporphyrin−Phthalocyanine Light-Harvesting Arrays

Light-harvesting arrays containing four porphyrins covalently linked to a phthalocyanine in a star-shaped architecture have been synthesized. Cyclotetramerization of an ethyne-linked porphyrin−phthalonitrile in 1-pentanol in the presence of MgCl2 and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) afforded the all-magnesium porphyrin−phthalocyanine pentad in 45% yield. Similar reaction using Zn(OAc)2·2H2O afforded the all-zinc porphyrin−phthalocyanine pentad in 15% yield. Arrays with different metals (free base, Mg, Zn) in the porphyrin and phthalocyanine macrocycles have been prepared by selective demetalation and metalation steps. This approach provides rapid and convergent access to multiporphyrin−phthalocyanine arrays in diverse metalation states. The arrays are reasonably soluble in organic solvents such as toluene, THF, and CH2Cl2. The arrays exhibit strong absorption in the blue and red regions. Time-resolved and static optical measurements indicate that intramolecular singlet-excited-state energy transfer from the porphyrin to the phthalocyanine moiety is extremely rapid (picoseconds) and efficient. Ground-state electronic communication among the porphyrins is indicated by rapid hole/electron hopping among the metalloporphyrins in the arrays as detected by EPR measurements on the singly oxidized pentads. These physical measurements indicate that the porphyrin−phthalocyanine pentads possess favorable characteristics for light harvesting and other photonics applications.

A short entry into the pyrido[2,3-b]indole ring system. Synthesis of the tetracyclic segment of the marine antitumor agents: Grossularines-1 and -2

A new method for the synthesis of substituted pyrido[2,3-b] indoles (α-carbolines) (14, 27-31), featuring Pd-catalyzed cross coupling between pyridine and aniline derivatives and subsequent intramolecular cylization, has been developed. This method provided a highly convergent access to the tetracyclic segment (3) of the marine antitumor agents: grossularines-1 and -2 (1,2).