Vacuum liquid chromatography

Modifications of the method (dry-column chromatography, vacuum liquid chromatography, VLC, for example) are also of practical use for the rapid fractionation of plant extracts. VLC with a polyamide support has been reported for the separation of flavonol glycosides. ... 

Azido-2-methylpropanoic Add a-Azido Acids from a-Bromo Adds and NaN3 i i 2-Bromo-2-methylpropanoic acid (4.96 g, 29.7 mmol) and NaNj (2.88 g, 44.3 mmol) were mixed in dry DMF (50mL) and stirred under argon for 2d. The mixture was concentrated, redissolved in HjO (30 mL) and acidified to pH 2 with 3 M HCl. The aqueous phase was extracted with CHCI3 (3 x 30 mL) and the organic phase was dried, concentrated, and purified by vacuum liquid chromatography (VLCI " ) (AcOH/EtOAc/heptane 5 20 75) yield 2.68 g (70%). 

Sonication and liquid chromatography are a rapid pair of techniques for extraction and fractionation of plant material. The method combines extraction by sonication with a mixture of nonmiscible solvents, rapid preseparation of the crude extract by vacuum-liquid chromatography (silica gel 60H), and separation by preparative, reversed-phase HPLC or classical liquid chromatography with polyvinylpyrrolidone. 

Loading of the sample and speed of operation are poor compared to vacuum liquid chromatography. 

Pelletier, S. W., Chokshi, H. P., and Desai, H. K. (1986) Separation of diterpenoid alkaloid mixtures using vacuum liquid chromatography. J. Nat Prod 49,892-900... 

Vacuum liquid chromatography Adsorption a b [Unpublished reports]... 

Forskolin is a well-known activator of adenylyl cyclase, obtained from the roots of Coleus forskohlii. Several methods were reported for the isolation of pure forskolin from the roots of C. forskohlii. The various methods of isolation, the purity, and yield of isolated forskolin are described. The methods included column chromatography, vacuum liquid chromatography, charcoal... 

Recently, several online separation and detection systems are available for the qualitative and quantitative analysis of elute/solutes from the columns to speed up the isolation process. Using this principle, a lot of separation techniques were evolved including (1) flash chromatography (FC), (2) vacuum liquid chromatography (VLC), (3) preparative planar chromatography, (4) low-pressure LC (LPLC), (5) medium-pressure LC (MPLC), and (6) high-pressure LC (HPLC). 

Coll, J.C. and Bowden, B.F. 1986. The Application of Vacuum Liquid Chromatography to the Separation of Terpene Mixtures. Journal cf Natural Products, 49, (5), 934-936. 

Targett, N.M., Kilcoyne, J.P., and Green, B. 1979. Vacuum liquid chromatography an alternative to common chromatographic methods. The Journal of Organic Chemistry, 44, (26), 4962 964. 

Well established techniques 170, 171) for the isolation and separation of depsides from mixtures of lichen acids include fractional crystallization, preparative layer chromatography and column chromatography. Vacuum liquid chromatography 124) provided a convenient and efficient modification of the latter technique and was used in separating a complex mixture of tridepsides from the crude extracts of Parmelia damaziana. 

Di-O- methylgyrophoric acid OMe H OMe H OH CO2H OH Parmelia damaziana Vacuum liquid chromatography Spectral data, synthesis 124)... 

Scheme 7 Representative synthesis of di- and tri-Boc protected spermine (167b, 168b). The Tfa group (142) is used for temporary blocking the primary amines. Di- and tri-Boc-spermine are obtained in 18% and 43% yield after chromatographic purification by vacuum liquid chromatography. Reagents and conditions a 1.2 eq Tfa-OEt, MeOH, -50 °C b B0C2O, MeOH, 0 °C c NaOHconc/H20 [216].

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