9096
S. Gogoi, N. P. Argade / Tetrahedron 60 (2004) 9093–9097
and dried in vacuo. The residue was purified by silica gel
column chromatography using a mixture of ethyl acetate
and petroleum ether (1:4) to furnish 10.
nmax 1788, 1379, 1105 cmK1. Anal. Calcd for C8H12O4: C,
55.81; H, 7.02. Found: C, 55.72; H, 6.97.
4.1.10. 3,4-Dihydroxy-3-methyl-dihydro-furan-2-one
(14). To a stirred solution of lactone 13 (20 mg,
0.12 mmol) in water (1 mL) was added trifluroacetic acid
(0.01 mL) at 0 8C. The reaction mixture was allowed to
warm up to room temperature and further stirred at room
temperature for 24 h. The reaction mixture was then
concentrated and dried in vacuo to obtain pure 14.
Compound 10. 2.22 g (92% yield); faint yellow thick oil; 1H
NMR (CDCl3, 200 MHz) d 1.41 (s, 3H), 1.55 (s, 3H), 1.66
(s, 3H), 3.70 (s, 3H), 3.78 (s, 3H), 4.40 (s, 1H); 13C NMR
(CDCl3, 50 MHz) d 22.2, 26.1 (2 gem-methyl carbons),
51.8, 51.9, 81.5, 82.9, 111.0, 167.2, 171.1; IR (CHCl3) nmax
1761, 1744 cmK1. Anal. Calcd for C10H16O6: C, 51.72; H,
6.95. Found: C, 51.66; H, 6.89.
Compound 14. 15 mg (97% yield); faint yellow thick oil; 1H
NMR (CD3OD, 200 MHz) d 1.37 (s, 3H), 4.04 (dd, JZ2,
4 Hz, 1H), 4.13 (dd, JZ2, 10 Hz, 1H), 4.43 (dd, JZ4,
10 Hz, 1H); 13C NMR (CD3OD, 50 MHz) d 21.6, 73.3, 74.4,
4.1.7. Potassium 2,2,4-trimethyl-[1,3]dioxolane-4-carb-
methoxy-5-carboxylate (11). To a solution of diester 10
(2.00 g, 8.62 mmol) in methanol (15 mL) was added a
solution of KOH (484 mg, 8.62 mmol) in methanol (10 mL)
in a drop wise fashion with constant stirring at room
temperature. The reaction mixture was stirred for 1 h and
concentrated in vacuo. The residue obtained was washed
with CHCl3 (10 mL!2) to obtain pure 11.
74.6, 180.4; IR (CHCl3) nmax 3421, 1778, 1215, 758 cmK1
.
Anal. Calcd for C5H8O4: C, 45.46; H, 6.10. Found: C, 45.45;
H, 6.19.
4.1.11. Potassium 2,3,4-trihydroxy-2-methylbutanoate
(1). To a solution of lactone 14 (10 mg, 0.08 mmol) in
water (1 mL) was added KOH (4 mg, 0.08 mmol). The
reaction mixture was stirred for 10 min and concentrated in
vacuo to obtain 1.16
Compound 11. 2.20 g (w100% yield); white solid; mp 234–
236 8C; H NMR (D2O, 200 MHz) d 1.33 (s, 3H), 1.46 (s,
1
3H), 1.55 (s, 3H), 3.59 (s, 3H), 4.33 (s, 1H); 13C NMR (D2O,
50 MHz) d 24.9, 28.2, 28.4, 55.3, 85.7, 86.6, 113.3, 175.7,
176.5; IR (KBr) nmax 1736, 1628 cmK1
.
Compound 1. 1H NMR (D2O, 200 MHz) d 1.34 (s, 3H), 3.57
(m, 2H), 3.80 (m, 1H); 13C NMR (D2O, 50 MHz) d 25.0,
64.9, 78.5, 79.5, 183.5.
4.1.8. 2,2,4-Trimethyl-[1,3]dioxolane-4,5-dicarboxylic
acid 4-methyl ester (12). The salt 11 (2.00 g, 7.81 mmol)
was acidified to pH 5 with minimum amount of 2 N HCl and
extracted with ethyl acetate. The organic layer was washed
with brine, dried over Na2SO4 and concentrated in vacuo to
obtain 12.
4.1.12. 2,2,6a-Trimethyl-dihydro-furo[3,4-d][1,3]dioxol-
4-one (15). To the suspension of salt 11 (100 mg,
0.39 mmol) in THF (7 mL) was added LiBH4 (34 mg,
1.56 mmol) at 0 8C. The reaction mixture was then stirred at
room temperature for 6 h. The reaction was quenched with
water and the reaction mixture was concentrated in vacuo.
The aqueous layer was acidified with minimum amount of
dilute HCl and extracted with ethyl acetate (15 mL!3). The
organic layer was washed with brine, dried over Na2SO4,
concentrated and dried in vacuo to obtain pure 15.
1
Compound 12. 1.12 g (66% yield); colourless thick oil; H
NMR (CDCl3, 200 MHz) d 1.37 (s, 3H), 1.48 (s, 3H), 1.62
(s, 3H), 3.66 (s, 3H), 4.36 (s, 1H), 9.15 (bs, 1H); 13C NMR
(CDCl3, 50 MHz) d 22.5, 26.5, 26.6, 52.3, 81.5, 83.5, 111.7,
171.3, 171.7; IR (CHCl3) nmax 1744, 1720 cmK1. Anal.
Calcd for C9H14O6: C, 49.54; H, 6.47. Found: C, 49.39; H,
6.51.
Compound 15. 40 mg, (60% yield); white crystalline solid;
mp 42–44 8C; H NMR (CDCl3, 200 MHz) d 1.41 (s, 3H),
1
1.49 (s, 3H), 1.54 (s, 3H), 4.15 (d, JZ12 Hz, 1H), 4.45 (d,
JZ12 Hz, 1H), 4.46 (s, 1H); 13C NMR (CDCl3, 50 MHz) d
21.9, 27.7, 28.5, 75.7, 79.6, 83.5, 114.1, 174.5; IR (CHCl3)
nmax 1788, 1383, 1217 cmK1. Anal. Calcd for C8H12O4: C,
55.81; H, 7.02. Found: C, 56.01; H, 7.07.
4.1.9. 2,2,3a-Trimethyl-dihydro-furo[3,4-d][1,3]dioxol-
4-one (13). To a solution of acid 12 (100 mg, 0.46 mmol)
in THF (5 mL) was added borane–dimethylsulfide complex
(38.3 mg, 0.50 mmol) in THF (1 mL) in a drop wise fashion
with constant stirring at K8 8C. The reaction mixture was
then allowed to warm up to room temperature and further
stirred at room temperature for 36 h. The reaction was
quenched with water (3 mL), and the reaction mixture was
concentrated in vacuo. The obtained residue was stirred
with diethyl ether (40 mL). The organic layer was washed
with brine and dried over Na2SO4, concentrated and dried in
vacuo. The crude product was purified by silica gel column
chromatography using a mixture of ethyl acetate and
petroleum ether (1:4) to furnish 13.
4.1.13. 3,4-Dihydroxy-4-methyl-dihydro-furan-2-one (7).
To a stirred solution of lactone 15 (20 mg, 0.12 mmol) in
THF (2 mL) and water (0.5 mL) was added trifluroacetic
acid (0.01 mL) at 0 8C. The reaction mixture was allowed to
warm to room temperature and further stirred at room
temperature for 3 h. The reaction mixture was then
concentrated and dried in vacuo to obtain pure 7 in 78%
yield. Analytical and spectral data matched with that of
compound 7, obtained from 5.
Compound 13. 39 mg, (50% yield); colourless thick oil; 1H
NMR (CDCl3, 200 MHz) d 1.42 (s, 3H), 1.47 (s, 3H), 1.57
(s, 3H), 4.32 (dd, JZ4, 10 Hz, 1H), 4.44 (dd, JZ0, 10 Hz,
1H), 4.49 (dd, JZ0, 4 Hz, 1H); 13C NMR (CDCl3, 50 MHz)
d 18.4, 26.6, 26.9, 68.9, 80.3, 81.4, 113.0, 176.7; IR (CHCl3)
Acknowledgements
S. G. thanks CSIR, New Delhi, for the award of a research