Alternative synthesis of cystothiazole A

Palladium-catalyzed methoxycarbonylation of (−)-(2R,3S)-1-tert-butyldimethylsiloxy-3-methyl-2-methoxypenta-4-yne 9 derived from (2R,3S)-epoxy butanoate 5 gave the acetylenic ester 10, which was treated with MeOH in the presence of Bu₃P to afford selectively (Z)-β-methoxy acrylate congener 11 in 86% yield. Treatment of (Z)-11 with 99.8% enrichment of CDCl₃ followed by consecutive desilylation and oxidation afforded the left-half aldehyde (+)-2. The overall yield (10 steps from 5; 23%) of (+)-2 via the present route was improved in comparison to that (10 steps from 5; 10%) of the previously reported route. By applying the modified Julia's coupling method, selectivity (E/Z=14:1) of the (E)-form (cystothiazole A 1) against the (Z)-form was improved in comparison to the Wittig method (E/Z=4:1 to 6.9:1).     

Alternative total synthesis of (+)-aspicilin

The total synthesis of an 18-membered polyhydroxylated macrolide (+)-Aspicilin was accomplished starting from commercially available enantiopure propylene oxide and D-(+)-gluconolactone by asymmetric synthetic approach. The key reactions involved are Witttig reaction, Sharpless asymmetric dihydroxylation, and Yamaguchi macrolactonization.     

Alternative esters in the synthesis of ZD0947

Alternatives to the original iso-borneol and allyl esters were investigated in the synthesis of ZD0947 (1). Homologous allylic esters were prepared in higher yields and were more readily purified than for the existing route, but offered no further benefits later in the synthesis. However, the PNB-substituted ester series provided crystalline intermediates, higher yields and simplified isolations through-out, and utilised a heterogeneous hydrogenation, thus reducing the residual catalyst levels.     

Alternative approaches to the synthesis of polyfluoroalkyl-containing 1-methyl-4-nitrosopyrazoles

Russian Chemical Bulletin - We studied different approaches to the synthesis of polyfluoroalkyl-containing 1-methyl-4-nitrosopyrazoles, which are based on the cyclization of...     

Alternative synthesis and crystal structure of a [2]boraferrocenophane

The [2]boraferrocenophane [(η⁵-C₅H₄)-B(NMe₂)-B(NMe₂)-(η⁵-C₅H₄)Fe] (1) was obtained from the reaction of FeCl₂ and (Me₂N)₂B₂(η¹-C₅H₅)₂ as a diborane(4) based ligand precursor in very good yields and fully characterized in the solid by single crystal X-ray diffraction.     

Alternative procedure for the synthesis of Mansonone F and Biflorin precursor

Synthetic studies on Mansonone F and Biflorin are described. Synthesis of ketone 12 has been achieved by utilizing tetrahydronaphthalene 8 which in turn was prepared from the 5-methoxy-alpha-tetralone 3. The conversion of 8 into ketone 12 was accomplished in four steps (O-alkylation with ethyl bromoacetate, dehydrogenation, alkaline hydrolysis and cyclization with phosponate ester).     

Alternative energy input: mechanochemical, microwave and ultrasound-assisted organic synthesis

Microwave, ultrasound, sunlight and mechanochemical mixing can be used to augment conventional laboratory techniques. By applying these alternative means of activation, a number of chemical transformations have been achieved thereby improving many existing protocols with superior results when compared to reactions performed under traditional conditions. The purpose of this critical review is to highlight the advances in this general area by presenting such newer applications in organic synthesis (175 references).     

Alternative strategies for the stereoselective synthesis of enantioenriched 6-arylated piperidin-2-ones

Two alternative synthetic approaches to a variety of enantioenriched 6-arylated piperidin-2-ones have been developed. The first one is based on the hydrogenation of suitably arylated chiral cyclic enehydrazides. The second approach relies on the asymmetric catalytic hydrogenation of the corresponding N-alkylated precursors.     

Alternative solvents for elevated-temperature solid-phase parallel synthesis. Application to thionation of amides

A new class of higher-boiling solvents was investigated for elevated-temperature solid-phase parallel synthesis. Extremely low vapor pressures at high temperature and a broader range of solvent effect tuning make this new class of solvents an ideal choice for high-temperature parallel solid-phase synthesis. Benzyl benzoate is identified as a superior high-boiling solvent for parallel solid-phase Lawesson's thionation reactions.     

Alternative synthesis of enantiomeric 1-diphenylphosphino-2-dimethylaminomethylferrocene (Kumada's ligand)

A novel facile synthesis of enantiomeric 1-diphenylphosphino-2-dimethylaminomethylferrocene (III), an important ligand for asymmetric catalysis using metal complexes, has been developed. This substance is prepared in a two-step procedure starting with dimethylaminomethylferrocene (I), in 40% overall yield. The absolute configuration and maximum optical rotation of III are determined through the correlation with the previously described cyclopalladated amine derived from I.     

Alternative route towards the convergent synthesis of a human purine nucleoside phosphorylase inhibitor—forodesine HCl

Forodesine HCl is being investigated as a potential target for the control of T-cell proliferation. Herein we present an alternative route for the synthesis of the target molecule with addition of lactam to the lithiated deazahypoxanthine (generated in situ). The lactam was synthesized in five steps starting from l-pyroglutamic acid.     

Alternative simple and effective synthesis of (di)benzoxanthones and their functions toward fluorescent dyes

(Di)benzoxanthones possessing additional benzene units on one or both sides of xanthone were prepared via dehydration of the corresponding dihydroxybenzophenone, where a catalytic amount of K₂CO₃ dramatically increased the yields. Chemical transformations of the versatile carbonyl groups of (di)benzoxanthones could derive fluorescent materials.     

Sequence of alkylation of cyclohexane-1, 3-dione. Alternative synthesis of (±)-Angustione

A method is proposed for introducing one, two, or three alkyl substituents into positions 4 and 6 of the cyclohexane-1, 3-dione molecule by successive alkylation under the action of strong bases. (±)-Angustione (a natural β-diketone) has been synthesized. Institute of Bioorganic Chemistry, Academy of Sciences of the Belorussian SSR, Minsk. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 460–463, July–August, 1991.     

Alternative biofuels

This study presents the experimental results for the dimethyl ether (DME) + propane system obtained using the Burnett method. The apparatus was calibrated using helium. PVTx measurements were taken for four isotherms (344, 354, 364, and 375 K), performing 16 Burnett expansions in pressures ranging from about 3,000 to 70 kPa. The second and third virial coefficients were derived from experimental results. The experimental uncertainty in the second and third virial coefficients was estimated to be within ±5 cm³/mol and ±1,000 cm⁶/mol², respectively.