Low noise amplification of an optically carried microwave signal: application to atom interferometry

In this paper, we report a new scheme to amplify a microwave signal carried on a laser light at λ=852 nm. The amplification is done via a semiconductor tapered amplifier and this scheme is used to drive stimulated Raman transitions in an atom interferometer. Sideband generation in the amplifier, due to self-phase and amplitude modulation, is investigated and characterized. We also demonstrate that the amplifier does not induce any significant phase-noise on the beating signal. Finally, the degradation of the performances of the interferometer due to the amplification process is shown to be negligible.     

Simple,Safe, Large Scale Synthesis of 5-Arylmethyl-2,2-dimethyl-1,3-dioxane-4,6-diones and 3-Arylpropanoic Acids

Reaction of aryl aldehydes with Meldrum's acid 2 in the presence of formic acid and triethylamine gives 5-arylmethyl Meldrum's acid derivatives 4 at room temperature, whereas at 80–100°C 3-arylpropanoic acids 5 are formed.     

The Synthesis of 17-Ester of Corticosteroids Protection of 11β-Hydroxyl by the Trimethylsilyl Group

17–Esters of corticosteroids have received considerable attention due to their high topical anti-inflammatory activity. one of the best known is betamethasone 17-valerate which is widely used against a variety of skin diseases². The relatively simple compound, hydrocortisone 17–butyrate (3a)³ proved to be as active topically as the more sophisticated corticosteroids such as triamcinolone acetonide, while its systemic activity is of the same order as that of hydrocortisone⁴.     

Multicompartment micelles from silicone-based triphilic block copolymers

An amphiphilic linear ternary block copolymer was synthesised in three consecutive steps via reversible addition–fragmentation chain transfer polymerisation. Oligo(ethylene glycol) monomethyl ether acrylate was engaged as a hydrophilic building block, while benzyl acrylate and 3-tris(trimethylsiloxy)silyl propyl acrylate served as hydrophobic building blocks. The resulting “triphilic” copolymer consists thus of a hydrophilic (A) and two mutually incompatible “soft” hydrophobic blocks, namely, a lipophilic (B) and a silicone-based (C) block, with all blocks having glass transition temperatures well below 0 °C. The triphilic copolymer self-assembles into spherical multicompartment micellar aggregates in aqueous solution, where the two hydrophobic blocks undergo local phase separation into various ultrastructures as evidenced by cryogenic transmission electron microscopy. Thus, a silicone-based polymer block can replace the hitherto typically employed fluorocarbon-based hydrophobic blocks in triphilic block copolymers for inducing multicompartmentalisation.     

Phase Transfer Promoted Ruthenium Oxide Oxidations of Carbohydrates II

ABSTRACT

The use of a phase transfer catalyst, benzyltriethylammonium chloride (BTEAC), is described in conjunction with the ruthenium dioxide/periodate : water/chloroform system for the oxidation of carbohydrate alcohols to the corresponding ketone, aldehyde, or carboxylic acid. The method was found to be applicable to carbohydrates appropriately protected as acetals, ethers, or containing a benzoyloxy group not positioned to readily undergo β-elimination. While the method was very suitable for the oxidation of carbohydrate secondary alcohols to ketones, it was found to be less suitable for the oxidation of a carbohydrate primary alcohol to the corresponding aldehyde or carboxylic acid. Evidence presented suggests that under the mildly basic conditions of the reaction, ruthenium tetraoxide is converted to ruthenate and perruthenate ions in the aqueous solution and then the perruthenate ion is carried by the phase transfer catalyst into the organic layer where oxidation of the substrate occurs. A number of examples illustrating the scope of the method are presented.     

New Heterocyclic Analogues of Anthracycline Antibiotics

ABSTRACT

Synthetic approaches to anthracycline antibiotic analogues in which the nitrogen atom of the carbohydrate portion is incorporated into a 1, 2, 3-triazolyl moiety were investigated. By using methyl 6-azido-2, 6-dideoxy-β-D--arabino-hexopyranoside and methyl 6-azido-2, 3, 6-tricdeoxy--α-L-arabino-hexopyranoside, the corresponding glycosides (16 a, b - 18 a, b) of carminomycinone and daunomycinone were prepared. The desired heterocyclic system was developed directly with the C-3′ and C-6′ azido anthracyclines by means of a cycloaddition process to give 7-0-[6′-(4, 5--dicarboethoxy-l, 2, 3-triazolyl)-2′, 6′-dideoxy-β-D-arabino--hexopyranosyl]-carminomycinone (23) and -daunomycinone (22), and 3′-(4, 5-dicarboethoxy - l, 2, 3-triazolyl)-4′ -epi-daunomycin (24).     

The Crystal and Molecular Structure of the Smectogenic Compound 5-Hexyl-2-(4-bromophenyl)-1,3-dioxane

The title compound with the formula C₆H₁₃ C₄O₂H₆ C₆H ₄Br (HBPD) crystallizes in the monoclinic space group C 2/c with lattice parameters a = 28.48 Å, b = 5.71 Å, c = 20.19 Å, β = 97.4° and molecules per unit cell. The structure has been solved by the heavy atom method and refined to a final R value of 0.094. – The HBPD molecules adopt a fully stretched form, both the alkyl and phenyl substituent are in equatorial position with respect to the chair-shaped dioxane ring. The orientation of the phenyl group is an intermediate between the perpendicular and parallel conformation. The molecules show a nearly perfect parallel arrangement in the crystal lattice.     

Large-scale production of polypropylenimine dendrimers

The synthesis and characterization of a new series of polypropylenimine dendrimers is reported. Using a repetition of the sequence of a Michael addition to a primary amine, followed by a heterogeneously catalyzed hydrogenation, ultra-pure polypropylenimine macromolecules with molecular weights up to 6912 are synthesized. The reaction sequence allows the preparation of these dendrimers at very large scales, whilst the availability of a simple purification in the sequence affords ultra-pure samples. The polypropylenimine dendrimers are fully characterized; apart from the first 0.5 generation they are all oils, possess a Tg in the range from −90 to −40 °C, are unexpectedly stable, and their intrinsic viscosity drops after generation 4.