The characteristics of the new chiral stationary phase heptakis(2,3-di-O-met hyl-6-0-tert-butyldimethylsilyl)-fl-cyclodextrin are outlined and compared with permethyl-and perethyl-P-cyclodextrins. Column C: . T b 7 20 25 min. 20 25 min.Figure 6 Separation of the enantiomers of lavandulyl acetate on columns A and C (coated with 15 and 5 0 % of DIME-6-TBDMS-P-CD in OV-1701-vi, respectively): conditions as for Figure 3.phases. Figure 7 shows a test for chiral GC separations on a micro preparative scale, the separation of 1-(2-methoxypheny1)ethanol on a 0.54 mm i.d. fused silica wide bore column. In this instance SE-52 was used as solvent for the modified cyclodextrin. ConclusionThe introduction of the bulky TBDMS groups slightly changes, but does not reduce, the chiral selectivity, and it is, furthermore, evident that the chiral selectivity and versatility of this new chiral stationary phase are at least as high as those of PME-P-CD.

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SummaryHeptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-P-cyclodextrin proves to be a versatile chiral stationary phase for the direct differentiation of aroma-relevant enantiomers.

Enantioselective GC analysis of 4-ethyloctanoic and 4-methylheptanoic acid, using heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-~-cyclodextrin as the chiral stationary phase, is described and the sensory properties of several 4-alkyl-branched acids, using gas chromatography-olfactometry (GC-0) equipment and octakis(2,3-di-O-methy1-6-tert-butyldimethylsily1)-y-cyclodextrin as the stationary phase, are evaluated. The chirospecific analysis of various 2-, 3-, and 4-alkyl-branched acids from commercially available Roman chamomile (Chamuemelum nobile (L.) Allioni), Parmesan cheese, and subcutaneous mutton adipose tissue, using either GC-GC (MDGC) or GC-MS analytical methods, is described. In part 1 of this investigation the synthesis of enantiopure alkyl-branched acids is reported.' Using these reference substances and heptakis(2,3-di-O-methyl-6-O-tevt-butyldimethyl sily1)-p-cyclodextrin (DIME-6-TBDMS-P-CD) or octakis(2,3-(DIME-6-TBDMS-y-CD) as chiral stationary phases in capillary gas chromatography, the direct chirospecific analyses of all 2-, 3-and 4-alkyl-branched acids investigated are performed. The enantiomeric distribution of these acids from Parmesan cheese, mutton, and Roman chamomile (Chumuemelum nobile (L.) Auloni syn. Anthemis nobilis L. ) is investigated. Furthermore, the sensory properties of alkylbranched acids' enantiomers are evaluated using GColfactometry equipment. MATERIALS AND METHODS Capillary Gas ChromatographyCarlo Erba GCs, models Mega HT and Fractovap series 4160, equipped with FIDs were used. The carrier gas wash H2 (50 cdsec), and split injection was employed. The syntheses of heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-P-cyclodextrin (DIME-6-TBDMS-(3-CD) and octakis(2,3-&-O-methyl-6-O-tert-butyldimethylsilyl)-y-cyclodextrin (DIME-6-TBDMS-y-CD) and the preparation of capillary columns have been described elsewhere. , coated with a solution of 33% DIME-6-TBDMS-y-CD in SE 52 (film thickness: 0.48 pm); carrier gas He, 40 kPa; injector temperature: 230"C, split injection; temperature program: 40W5 min isothermal/l0"C/ min lOO"C/l"C/min 130"C/3"C/min 235°C. Column II: A fused silica column (40 m x 0.32 mm id.), coated with a solution of 30% DIME-6-TBDMS-P-CD in SE 52 (film thickness: 0.50 Fm); camer gas: helium 35 kPa; injector temperature: 230°C; split injection; temperature program: 100°C/5 min isothermaV1.5"C/min 230°C. Enantioselective MultidimensionalGas Chromatography A Siemens SiChromat 2-8 double oven system with two independent temperature controls, two FIDs, and a "live switching" coupling piece ("live-T-piece"; Siemens AG, FRG) was employed. GC conditions: injector temperature: 250°C; detector temperature: 270°C. Precolumn system: a 30 m x 0.32 mm i.d. glass capillary column coated with SE-52, film thickness: 0.65 pm. Camer gas: hydrogen (150 kPa); temperature program: 60"C/5 min isothermaV5"C/ min 260°C. Main column system: a 30 m x 0.23 nun id. glass capillary column coated with 15% heptakis(2,3-di-O-methyl-6-O-tert-butyldi1nethylsilyl)-P cyclodextrin (DIM...

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