Preparative tic

A high degree of skill is required to draw a tic dropper across a line at r rase of the plate, applying a very thin and even line of the sample rtion, without damaging the silica. In between each application the. ent is allowed to dry before a further application is made, and this -T- is repeated until all the sample has been loaded. 

After running the plate (multiple elution is often required for good. ..Tiration), it is viewed under a uv lamp and the bands are marked with a pencil (it is very difficult to use prep tic for non-uv active compounds). 

Great skill is required to run preparative tics effectively, and even then sample obtained is often contaminated with significant quantities of sase and tic plate binding agent. Since there are now much better modem all scale separation techniques available, we do not recommend Treparative tic (see below foT details of preparative hplc and Chapter 12 for re on small scale flash chromatography). 

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JJalomycins. The halomydns are a group of four antibiotics produced by Micromotiospora halophytica and separated by partition chromatography on Chromosorb W coated with formamide. Further purification was accomplished using preparative tic. 

Dry clean tanshen rhizomes were powdered and extracted with hexane for three days at room temperature. The hexane solution was kept overnight and then filtered. After removal of the solvent a residue was obtained which was separated into seven colored fractions by column chromatography with silica gel. Miltirone was isolated by preparative tic from fraction 1 (light red) using hexane ethyl acetate (4 1) followed by benzene-acetone (20 1). The product obtained was recrystallized from ethylacetate, m.p. 100-101°C. Its structure was confirmed by mass spectrum, NMR, IR and UV spectra which agree quite closely with those of Ho et al [76], Miltirone showed antioxidant behavior comparable to that of the commonly used phenolics BHT and BEA [77], The antioxidant activity of miltirone in lard at 100°C was determined with a Rancimat. Miltirone and other related compounds may have the potential of being used as natural antioxidants in food and cosmetics. 

Momenteau s route to doubly-strapped porphyrins was easily adapted to produce compounds in which an axial base was incorporated into one of the straps Condensation of tetra(o-hydroxyphenyl)porphyrin (250) (mbcture of four isomers) with one equivalent of 1,12-dibromododecane gave a mixture of two singly-linked porphyrins, depending on whether adjacent (255), or opposite (254) meso-phenyl groups were linked. This mixture was reacted with 3,5-bis(3-bromopropyl)pyridine 256 and the desired cross trans-linked isomer 257 isolated by preparative tic (5% overall yield) (Scheme 77). A similar porphyrin 259 was prepared from a,p,a,p-tetra(o-aminophenyl)porphyrin (142) in this case the straps were tied to the porphyrin skeleton by amide linkages (Scheme 78). Following iron insertion and reduction, visible absorption and H-NMR spectra of both compounds were consistent with a five-coordinate high spin (S = 2) iron(II) complex. 

The partially purified anacardic acids, from both the resistant and susceptible plants were further cleaned up prior to hpic separation using Merck 20x20cm, 2mm thickness preparative tic plates. The compounds were applied to several plates as the dimethylated compounds (diazomethane, 30 minute treatment (fi.)), and run in the same two step solvent system described above. The plates were viewed at 254nm and the anacardic acid bands were cut and eluted from the silica using methylene chloride (3x30mL). The purified anacardic acids were then ready for separation by preparative hpIc. 

Phospholipids were isolated by preparative tic and were treated with phosphlipase A2. Released fatty acids and fatty acids from the lyso-lipids were resolved by argentation tic. Values for pepino are averages for 4 and 8 days and those for celery are averages for 2 and 4 days. = <1%. 

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