Diol plates

Diol plates are prepared by reaction of the silica matrix with a silane derived from glycerol. The resulting alcoholic hydroxyl residues bonded to the silica by a propyl spacer can operate with NP- or RP-TLC mechanisms, depending on the mobile phase and solutes. Polar compounds show reasonable retention by hydrogen bond and dipole-type interactions in the former mode, and in the RP mode retention is low but higher than with amino layers. 

Enantiomers of j8-blocking drugs have been separated on diol plate with dichloromethane and achiral counter ion, A -benzyloxycarbonylglycyl-L-proline as mobile phase additive [75]. 

Hydroxyandrosta-4,6-dien-3-one. A suspension of 42 g of crude androsta-4,6-diene-3j ,17j -diol in 2000 ml of chloroform is treated with 250 g of activated, manganese dioxide. The mixture is then shaken vigorously for 15 min in a stoppered flask. The mixture is filtered and the manganese dioxide washed well with chloroform in order to elute material which initially remains adsorbed on the solid phase. The filtrate is concentrated to a pale yellow, crystalline residue. Recrystallization from acetonitrile gives 38 g (90%) of 17/ -hydroxyandrosta-4,6-dien-3-one as plates mp 211-214°. 

A combinatorial approach for biocatalytic production of polyesters was demonstrated. A library of polyesters were synthesized in 96 deep-well plates from a combination of divinyl esters and glycols with lipases of different origin. In this screening, lipase CA was confirmed to be the most active biocatalyst for the polyester production. As acyl acceptor, 2,2,2-trifluoroethyl esters and vinyl esters were examined and the former produced the polymer of higher molecular weight. Various monomers such as carbohydrates, nucleic acids, and a natural steroid diol were used as acyl acceptor. 

This requires 3-5 hr. Progress of this hydrolysis can be monitored by thin layer chromatography on 0.25-nm silica gel 60 plates eluted with 50% ethyl acetate/hexanes Rf ketal 0.59, Rf diol 0.21. 

Other agents used to impregnate keiselguhr include formamide and propan-1,2-diol. In the case of these impregnating agents, the mobile phases used to develop the treated plates have to be of low polarity to avoid washing the agent off the plate. 

The reaction may be followed by thin-layer chromatography. The ratio of the Rf values for cyclohexene and c/s-diol 2 is 2 1 (commercial silica gel plates, ethyl acetate). The plates are best visualized by first spraying with 1 % aqueous potassium permanganate, then with methanolic sulfuric acid, followed by charring with heat. The checkers found that, if the procedure is followed exactly, monitoring the reaction by thin-layer chromatography is unnecessary. 

Figure 4.3 Chimeric hammerhead ribozyme structure. The ribozyme structure was computer modeled after the work of Pley et al. (1994). The yellow ribbon (backbone) and bases depict the catalytic core of the ribozyme, while the green ribbon (backbone) and bases depict the binding arms, which in this case are DNA from the work of Taylor etal. (1992). The magenta bases and ribbon (backbone) are the target RNA. The orange ribbon depicts the backbone of stem II, which can be minimally reduced to four propane diols and one G C base pair (J.Rossi and P.Swiderski, unpublished data). The blue ribbon represents the target backbone at the site of ribozyme-mediated cleavage, (see Color Plate 2)...

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