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Cho, Song, and Jang
Ph2SiH2 (97 mg, 0.53 mmol) in benzene (1 mL) under argon was heated to
reflux for 5 min, and then AIBN (22 mg, 0.13 mmol in 0.5 mL of benzene)
was added through the syringe pump to the reaction mixture for 1 h. The
reaction mixture was diluted with CH2Cl2 and washed with water. The
organic layer was dried over anhydrous MgSO4. After evaporation of
the solvent, the residue was separated by column chromatography on
silica gel (eluent: hexanes/EtOAc, 9:1) to afford 60 mg (93%) of 1b. oil;
25
D
½a þ10.5ꢀ (c ¼ 1.1, EtOH) (lit.[5] þ8.0ꢀ (c ¼ 1, CH2Cl2)); 1H NMR
(500 MHz, CDCl3) ꢀ 0.93 (t, J ¼ 7 Hz, 6H), 1.20–1.73 (m, 8H),
2.78–2.84 (m, 2H), 3.24 (d, J ¼ 5.4 Hz, 1H), 4.05–4.28 (m, 4H),
4.41–4.56 (m, 1H). 13C NMR (125 MHz, CDCl3) ꢀ 13.7, 19.1, 30.6, 38.9,
65.0, 65.9, 67.4, 173.6, 173.6. MS m/z (relative intensity) 246 (Mþ, 1),
192 (1), 173 (8), 155 (1), 145 (32), 117 (15), 89 (100), 71 (21), 57 (32).
(R,R)-Dibutyl 1,3-dioxolane-4,5-dicarboxylate (1c): Oil; ½a ꢁ0.02ꢀ
25
D
1
(c ¼ 1.0, CHCl3); H NMR (500 MHz, CDCl3) ꢀ 0.94 (t, J ¼ 6.9 Hz, 6H),
1.37–1.41 (m, 4H), 1.62–1.68 (m, 4H), 4.21 (t, J ¼ 6.5 Hz, 4H), 4.78 (s, 2H),
4.96 (d, J ¼ 1.2 Hz, 1H), 5.21 (d, J ¼ 1.2 Hz, 1H). 13C NMR (125 MHz,
CDCl3) ꢀ 13.8, 19.2, 30.6, 65.8, 77.6, 92.9, 168.4. MS m/z (relative
intensity) 274 (Mþ, 2), 244 (3), 174 (36), 157 (26), 144 (14), 117 (91),
101 (18), 88 (100), 71 (15), 57 (52).
(R)-Diethyl malate (2b): Silica gel column chromatography (eluent:
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hexanes/EtOAc, 6.5:3.5): oil; ½a þ11.2ꢀ (c ¼ 0.95ꢀ, EtOH) (lit.[4b] þ9.7ꢀ
D
(c ¼ 1.25, EtOH)); 1H NMR (100 MHz, CDCl3) ꢀ 1.20–1.42 (m, 6H),
2.79–2.85 (m, 2H), 3.28 (d, J ¼ 5.3 Hz, 1H), 4.07–4.56 (m, 5H). MS m/z
(relative intensity) 190 (Mþ, 1), 161 (1), 145 (11), 127 (4), 117 (99), 99 (6),
89 (41), 71 (100), 55 (3).
(R)-Dimethyl malate (3b): Silica gel column chromatography (eluent:
25
hexanes/EtOAc, 5.5:4.5): oil; ½a þ9.6ꢀ (c ¼ 2.3, EtOH) (lit.[4e] þ9.5ꢀ
D
(c ¼ 2.20, EtOH)); 1H NMR (CDCl3) ꢀ 2.81–2.87 (m, 2H), 3.40 (d,
J ¼ 5.1 Hz, 1H), 3.72 (s, 3H), 3.82 (s, 3H), 4.45–4.60 (m, 1H). MS m/z
(relative intensity) 162 (Mþ, 1), 131 (6), 113 (5), 103 (100), 85 (2), 71
(89), 61 (39), 55 (3).
Typical procedure for reaction of cyclic thionocarbonates of (R,R)-
tartrates with PhSiH3: (R)-Dibutyl malate (1b): A solution of the cyclic
thionocarbonate of dibutyl (R,R)-tartrate 1a (100 mg, 0.33 mmol),
PhSiH3 (81 mL, 0.66 mmol) in benzene (1 mL) under argon was heated to
reflux, and then AIBN (21 mg, 0.13 mmol in 0.5 mL of benzene) was added
through the syringe pump to the reaction mixture for 50 min. The reaction
mixture was diluted with CH2Cl2, washed with water, and dried over
anhydrous MgSO4. After filtration and evaporation, the residue
was separated by silica gel column chromatography (eluent: hexane/
EtOAc, 9:1) to afford 77 mg (95%) of 1b.