1924 J. Org. Chem. 1992,57,1924-1926 cm-'; 'H NMR (CDCl,) zyxwvutsr S 1.45 [9 H, zyxwvuts 8, 0C(CHJ3] 1.75 (1 H, m, H-3), 2.20-2.30 (1 H, m, H-39, 2.50-2.75 (2 H, m, H-4 and zyxwvuts p- MeOPhCH), 3.18 (1 H, m, p-MeOPhCH'), 3.75 (3 H, 8, OCH,), 3.98 (1 H, t, J zyxwvu = 7.7 Hz, H-21, 5.88 (1 H, 8, NH), 6.76 (2 H, m, p-MeOArH), 7.15 (2 H, m, p-MeOArH); MS m/z 305 (M+,31), 249 (49), zyxwvutsrqp 248 (22), zyxwvutsrq 205 (100). Anal. Calcd for C1,H&04: C, 66.89; H, 7.59; N, 4.59. Found: C, 66.98; H, 7.32; N, 4.45. tert -Butyl (25 )-4&( (p -fluorophenyl)methyl)pyro- glutamate (7e): white solid (EtOAc-hexane) (95 zyxwvut mg, 65%); mp 105-106 "C; [.]%D +31.8' (c 0.66, MeOH); IR (KBr) 1720,1745 cm-'; 'H NMR (CDC1,) S 1.40 [9 H, 8, 0C(CH3),], 1.70-1.80 (1 H, m, H-3), 2.32-2.40 (1 H, m, H-3'), 2.50-2.68 (2 H, m, H-4 and p-FPhCH), 3.15 (1 H, dd, J = 3.9,11.8 Hz, p-FPhCH'), 4.02 (1 H, t, J = 7.6 Hz, H-2), 6.05 (1 H, s, NH), 7.02 (2 H, m, p-FArH), 7.13 (2 H, m, p-FArH); MS m/z 293 (M+,20), 238 (91,192 (100). Anal. Calcd for C1$Ia03F: C, 65.53; H, 6.87; N, 4.78. Found C, 65.84, H, 6.62; N, 4.59. Alkylation of la or l b with Benzyl Bromide. Compounds la (0.95 g, 3 mmol) and l b (285 mg, 1 mmol) were benzylated with benzyl bromide according to the procedure described in the literaturelo to give 8a and 8b, respectively. tert-Butyl (2S)-l-(benzyloxycarbonyl)-4a-(phenyl- methy1)pyroglutamate (Sa): white solid (EtOAc-hexane) (430 1740, 1792 cm-'; 'H NMR (CDCl,) 6 1.34 [9 H, 8, OC(CH3)3], 1.95-2.10 (2 H, m, H-3 and H-39, 2.55-3.05 (2 H, m, H-4 and PhCH), 3.25 (1 H, dd, J = 2.5, 12 Hz, PhCH'), 4.35 (1 H, dd, J = 4.5,6.5 Hz, H-2), 5.25 (2 H, 8, PhCHzO),7.30 (10 H, m, Arm; MS m/z 410 (M + 1,20), 409 (M+, 35), 353 (30), 319 (111,275 (35), 265 (20), 264 (15);91 (100). Anal. Calcd for CNHnNO5: C, 70.41; H, 6.6; N, 3.42. Found C, 70.82; H, 6.92; N, 3.1. tert -Butyl (2S)-l-( tert-butyloxycarbonyl)-4a-( phenyl- methy1)pyroglutamate (8b): white crystalline solid (150 mg, [9 H, 8, C(CH,),], 1.83-2.05 (2 H, m, H-3 and H-3'),2.5-2.95 (2 H, m, H-4 and PhCH), 3.25 (1 H, dd, J = 2.5, 12 Hz, PhCH'), 4.30 (1 H, dd, J = 5,6.6 Hz, H-2), 7.23 (5 H, m, ArH); 13CNMR (CDClJ 6 27.9,36.3,43.3,57.7,82.2,83.2,126.5,128.6,128.9,138.3, 149.4, 170.2, 174.3; MS m/z 375 (M+, 5). Anal. Calcd for N, 3.68. Removal of the Benzyloxycarbonyl Group from 8a. Re- moval of the benzyloxycarbonyl group from 8a (0.4 g, 1 mmol) using a simii procedure as described for 4 or 5 gave 6c (200 mg, 75%). Removal of the tert -Butyloxycarbonyl Group from 8b. 8b (0.23 g, 0.6 mmol) was deprotected with TFA-CH2C& amording to the literature procedurelo to give 6c (95 mg, 56%), identical in all respecte to the product obtained by the aldol pathway. Conversion of 6c and 7c to 8b and 9. To a solution of 6c or 7c (0.14 g, 0.5 "01) in dry CHzClz were added EhN (0.07 mL, 0.5 mmol), di-tert-butyl dimbonate (0.22 g, 1 mmol), and DMAF' (0.06 g, 0.5 mmol). The solution was stirred for 6-8 h at 25 'C under a Nz atmosphere. The volatiles were removed, and the residue was chromatographed on a column of Florisil(30% Et- OAc-hexane) to give 8b and 9, respectively. tert-Butyl (2S)-l-( tert-butyloxycarbonyl)-4~-(phenyl- methy1)pyroglutamate (9): white solid (EtOAc-hexane) (140 mg, 73%); mp 115-116 "C; [@D +3.57O (c 0.56, MeOH); IR (KBr) [9 H, 8, C(CH,)J, 1.72 (1 H, m, H-3), 2.25 (1 H, m, H-3'),2.46-2.75 (2 H, m, H-4 + PhCH), 3.28 (1 H, d, J = 12.4 Hz, Ph-CH'), 4.33 (1 H, dd, J = 5.9, 8.8 Hz, H-2), 7.18 (5 H, m, Arm; NMR (CDCld 6 26.5,27.9,36.9,44.5,58.1,82.2,83.4,126.6, 128.7,128.9, 138.6,149.5, 170.6,174.6; MS m/z 375 (M+, 4), 320 (43), 319 (65), 263 (151, 246 (221,219 (40), 174 (35), 91 (100). Anal. Calcd for N, 3.45. tert-Butyl(2S)-4a-(Phenylmethyl)-bt~oxoprolinats (10). To a solution of 6c (275 mg, 1 mmol) in dry THF was added Laweson's reagent (202 mg, 0.5 "01). The solution was stirred for 4 h at 25 'C. The volatiles were removed, EGO (25 mL) was added, and the mixture was poured into cold saturated sodium bicarbonate solution. The EGO layer was separated, and the aqueous layer was extracted twice with EGO. The EGO extract mg, 35%);mp 112-114 'C; [.]%D -59.2' (C 1.75, CHCld; IR (mr) 40%); mp 129-131 'c; [CY]=D -34.09' (C 0.4, MeOH); IR (mr) 1742,1800 ~m-'; 'H NMR (CDC13) 6 1.40 [9 H, s,OC(CH~)~], 1.49 Cz1HdO5: C, 67.2; H, 7.73; N, 3.73. Found C, 67.05; H, 8.15; 1745,1800 ~m-'; 'H NMR (CDCld S 1.45 [9 H, 8, OC (CH&], 1.50 CZiH&JOb: C, 67.20; H, 7.73; N, 3.73. Found: C, 66.95; H, 7.95; 0022-3263/92/1957-1924$O3.00/0 was washed with water, dried over Na2S04,concentrated, and chromatographed by flash chromatography using 20% EtOAc- hexane as eluent to afford compound 10 as a white crystalline solid (recrystallized from EtOAc-hexane) (195 mg, 67%); mp 88-91 'C; IR (KBr) 1750 cm-'; 'H NMR (CDC13) 6 1.35 [9 H, 8, 0C(CH3),], 2.15 (2 H, m, H-3 and H-3'), 2.65 (1 H, m, PhCH), 2.95-3.18 (1 H, m, H-4), 3.35 (1 H, dd, J = 2.5.12 Hz, PhCH'), 3.96 (1 H, dd, J = 5,9 Hz, H-2), 6.43 (1 H, s, NH), 7.14 (5 H, m, Arm; MS m/z 293 (M + 2,5), 292 (M + 1,201,291(M+,35), 237 (2), 236 (6), 235 (32), 234 (48), 202 (12), 91 (100). Anal. Calcd for C16Hz1N02S: C, 65.98; H, 7.21; N, 4.8. Found: C, 66.32; H, 7.17; N, 4.52. tertButyl(2S)-4a-(Phenylmethyl)prolinate (11). Sodium borohydride (912 mg, 24 "01) was added in portions to a solution of 10 (290 mg, 1 "01) and NiClZ-6Hz0 (2.2 g, 8 "01) in 50 mL of THF-MeOH (1:l) at 0 'C. The reaction mixture was stirred at room temperature until the starting material had disappeared as monitored by TLC; the reaction mixture was fiitered through Celite, concentrated, and chromatographed on a column of alu- mina to afford 11 (130 mg, 50%); IR (neat) 1742 cm-'; 'H NMR Hz, H-Ba), 1.95 (1 H, ddd, J = 8,5, 13 Hz, H-3j3), 2.32 (2 H, m, H-4 and PhCH), 2.58 (1 H, dd, J = 8, 11 Hz, H-5a), 2.66 (1 H, (5 H, m, Arm; zyxw '3c NMR (CDCld 6 27.8,36.4,39.4,40.4,52.5,60.0, 80.9, 125.8, 128.2, 128.5, 140.7, 174.4; MS m/z 262 (M + 1,44), 206 (91, 205 (4), 161 (35), 160 (95), 91 (go), 57 (100). Acknowledgment. We thank the Sophisticated In- struments Facility, Indian Institute of Sciences, Bangalore, India, for NOE studies, the Regional Sophisticated In- strumentation Centre, Lucknow, India, for spectral and analytical data, and Atul Products Ltd., Valsad, India, for a generous gift of benzyl chloroformate. Registry No. la, 81470-51-1;lb, 91229-91-3; 2c, 127949-784; 2d, 138858-32-9; 2e, 138858-33-0;2f, 13885834-1; 2g, 138858-352; 5d, 1388584@9; 6c, 127949-77-3; 6d, 138858-41-0; 6e, 138858-42-1; 7c, 138858-43-2;7d, 138858-44-3; 7e, 138858-454; 8a, 138858465; 8b, 127949-74-0; 9,13885847-6; 10,138858-487; 11,138858-49-8; Z-pGlu-OH, 32159-21-0; PhCHO, 100-52-7; 4-MeOC6H4CH0, MeOC6H4CH0, 591-31-1; PhCHzBr, 100-39-0; furan-2-carbox- aldehyde, 98-01-1. Supplementary Material Available: 'H NMR and in some cases lSC NMR spectra for compounds for which elemental analyses were not obtained (19 pages). Ordering information is given on any current masthead page. (CDClS) 6 1.45 [9 H, s,OC(CHJ~], 1.85 (1 H, ddd, J 10,9, 13 dd, J = 2.5, 7 Hz, PhCH'), 3.16 (1 H, dd, J = 7, 11 Hz, H-5/9), 3.72 (1 H, dd, J = 5.0,g.O Hz, H-2), 6.64 (1 H, 8, NH), 7.12-7.30 2h, 138858-36-3; 4c, 138858-37-4; 4d, 138858385; k, 138858-39-6; 123-11-5; 4-FC6H4CHO, 459-57-4; 4-C1C6H4CHO, 104-88-1; 3- Efficient Preparative Separation of Cso and C,@ Gel Permeation Chromatography of Fullerenes Using 100% Toluene as Mobile Phase Mark S. Meier* and John P. Selegue Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055 Received October 15, 1991 The scientific community is becoming increasingly in- terested in the chemistry and physics of the fullerene family of carbon allotropes.' A number of studies have uncovered interesting properties of Cm: rubidium- and potassium-doped Cm are high-temperature superconduc- tor~~-~ and Cmthin fiims display a number of interesting (1) Diederich, F.; Whetten, R. L. Angew. Chem., Int. Ed. Engl. 1991, (2) Chen, C.-C.; Kelty, S. P.; Lieber, C. M. Science 1991,253,886-888. 30,678-680. 1992 American Chemical Society