K. Edegger et al. / Tetrahedron 60 (2004) 583–588
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was flash-chromatographed using petroleum ether/ethyl
acetate (1:1) to give rac-3a as a yellow liquid (0.4 g, 73%).
3.3.3. 8-Chloro-2,6-dimethyl-oct-6E-en-2,3-diol (rac-3b).
Yield (0.2 g, 26%) from rac-3a (0.7 g, 3.7 mmol). 1H
NMR (CDCl3) d¼4.73 (d, J¼7.3 Hz, 2H), 3.95 (m, 2H), 2.1
(m, 4H), 1.67 (s, 3H), 1.22 (s, 3H), 1.18 (s, 3H).
1H NMR (360.13 MHz, CDCl3) d¼5.54 (t, J¼8.0 Hz, 1H),
4.09 (d, J¼8.0 Hz, 2H), 2.69 (t, J¼6.5 Hz, 1H), 2.20 (m,
2H), 1.74 (s, 3H), 1.65 (t, J¼7.0 Hz, 2H), 1.30 (s, 3H), 1.25
(s, 3H); 13C NMR (CDCl3) d¼141.6, 120.9, 63.7, 58.2, 40.7,
36.1, 27.0, 24.7, 18.7, 16.0.
3.3.4. 7-(7-Hydroxy-3,7-dimethyl-6-oxooct-2E-enyloxy)-
chromen-2-one (2c). Dess Martin reagent (20 mg,
0.05 mmol) was dissolved in anh. CH2Cl2 (5 mL) and
stirred at room temperature. Rac-2b (7 mg, 0.02 mmol) was
added and stirring was continued for 12 h. The crude
product was extracted with ether and sat. aq. NaHCO3, the
organic layer was dried (Na2SO4) and evaporated. The
crude product was purified by flash chromatography
(petroleum ether/ethyl acetate 1:1) to give 2c as a white
solid (5 mg, 77%). Mp 59–60 8C.
3.2.4. 7-(3,7,11-Trimethyldodeca-2E,6E,10E-trienyl-
oxy)-chromen-2-one (7-farnesyloxycoumarin, umbelli-
prenin, 5). To a stirred suspension of NaH (0.1 g,
4.2 mmol, 60% dispersion in mineral oil) in a mixture of
freshly destilled anhydrous THF (30 mL) and DMSO
(30 mL) under nitrogen 7-hydroxycoumarin (0.6 g,
3.7 mmol) was added at room temperature. After ten
minutes, 4 (1.1 g, 3.9 mmol) was added and the mixture
was refluxed for 2 h. The crude product was extracted with
0.5 M HCl (20 mL), H2O (100 mL) and ether (100 mL). The
combined organic layers were dried (Na2SO4) and evapor-
ated. The residue was flash chromatographed (petroleum
ether/ethyl acetate 1:1) and recrystallised from EtOAc/
petroleum ether (2/98) to give 5 as white crystals (1.3 g,
98%). Mp 45–46 8C.
1H NMR (CDCl3) d¼7.63 (d, J¼6.9 Hz, 1H), 7.37 (d,
J¼5.7 Hz, 1H), 6.83 (m, 2H), 6.25 (d, J¼5.4 Hz, 1H), 5.50
(t, J¼4.6 Hz, 1H), 4.60 (d, J¼4.4 Hz, 2H), 3.65 (s, 1H), 2.73
(t, J¼5.1 Hz, 2H), 2.42 (t, J¼4.5 Hz, 2H), 1.79 (s, 3H), 1.39
(s, 6H); 13C NMR (CDCl3) d¼213.5, 162.0, 161.3, 155.9,
143.3, 140.7, 128.8, 119.3, 113.3, 113.2, 112.6, 101.6, 76.6,
65.3, 33.8, 33.0,26.6, 17.0; HRMS calculated for C19H22O5:
330.1467 [Mþ]; found: 330.1432 [Mþ].
1H NMR (CDCl3) d¼7.63 (d, J¼9.47 Hz, 1H), 7.36 (d,
J¼8.47 Hz, 1H), 6.84 (m, 2H), 6.24 (d, J¼9.47 Hz, 1H),
5.47 (t, J¼5.93 Hz, 2H), 5.08 (m, 1H), 4.61 (d, J¼6.55 Hz,
2H), 2.1–1.9 (m, 8H), 1.77 (s, 3H), 1.68 (s, 3H), 1.60 (s,
6H); 13C NMR (CDCl3) d¼162.02, 161.20, 155.80, 143.29,
142.21, 135.64, 131.37, 128.51, 124.36, 123.56, 118.28,
113.08, 112.78, 112.28, 101.66, 65.54, 39.68, 39.57, 26.75,
26.19, 25.74, 17.73, 16.82, 16.08.
3.3.5. (R)-3,7-Dimethyloct-2E-en-1,6,7-triol (R)-(3c).
Biohydrolysis of rac-3a using Rhododoccus ruber DSM
44541 gave 3b in 79% ee (see below). The latter material
(154 mg, 748 mmol) was stirred in a mixture of 2,2-
dimethoxypropane (20 mL) and cat. p-toluenesulfonic acid
(20 mg). After 2 h, hydrolysis of the allylic chloride was
affected by addition of conc. NaOH (4 M, 10 drops) and
stirring was continued for 1 h. After the organic material
was extracted with ethyl acetate and evaporated, deprotec-
tion of the acetonide was achieved by addition of H2O
(20 mL) containing cat. p-toluenesulfonic acid (20 mg).
After 2 h, the solution was extracted with ethyl acetate and
the pruduct was purified by column chromatography
(petroleum ether/ethyl acetate 1:1) to give 3c (74 mg,
53%) showing an optical rotation of [a]2D0þ12.5 (c¼0.95,
CHCl3, 73% ee), which nicely corresponds to literature
data of [a]2D3þ17.4 (c¼1.4, CHCl3) for the (R)-
enantiomer.17
3.3. Synthesis of reference material
General procedure for the synthesis of reference material of
diols rac-1b–rac-3b. Epoxide rac-1a–rac-3a was dis-
solved in a mixture of H2O (5 mL) and THF (3 mL)
containing 3 drops of H2SO4 (conc.) and stirred at room
temperature for 2 h. The crude product was extracted with
EtOAc, neutralised with solid NaHCO3 and purified by flash
chromatography (petroleum ether/ethyl acetate 1:1). Thus
were obtained.
3.4. Biotransformations
3.3.1. 7-(10,11-Dihydroxy-3,7,11-trimethyldodeca-2E,
6E-dienyloxy)-chromen-2-one (rac-1b). Yield (30 mg,
98%) from rac-1a (30 mg, 0.08 mmol). 1H NMR
(CDCl3) d¼7.64 (d, J¼6.6 Hz, 1H), 7.36 (d, J¼6.2 Hz,
1H), 6.83 (dd, J¼6.0 Hz, 1H), 6.24 (d, J¼4.7 Hz, 1H), 5.73
(t, J¼4.2 Hz, 1H), 5.14 (t, J¼5.5 Hz, 1H), 4.61 (d,
J¼4.3 Hz, 2H), 3.39 (dd, J¼3.3 Hz, 1H), 1.76 (s, 3H),
1.63 (s, 3H), 1.20 (s, 3H), 1.16 (s, 3H).
3.4.1. Growth of strains. Rhodococcus ruber DSM 43338,
DSM 44541, DSM 44540, Rh. erythropolis DSM 312 and
Streptomyces sp. FCC 003 were maintained and grown on a
medium as described before.19 For Streptomyces venezuelae
ATCC 10712 (¼DSM 40230) medium #65 from DSMZ was
3.4.2. General procedure for biotransformation. Lyophi-
lised bacterial cells (50 mg) were rehydrated for 1 h in Tris–
HCl buffer (1 mL, 0.05 M, pH¼8.0) by shaking at 30 8C
with 130 rpm. Racemic epoxides rac-1a–rac-3a (5 mL)
were added, and the reaction was monitored by TLC. At
intervals of 24 and 48 h, aliquots of 0.4 mL were withdrawn
and extracted twice with EtOAc (0.4 mL each). To facilitate
phase separation, the cells were removed by centrifugation.
The combined organic layers were dried (Na2SO4) and
analysed by HPLC (Table 3).
3.3.2. 7-(6,7-Dihydroxy-3,7-dimethyloct-2E-enyloxy)-
chromen-2-one (rac-2b). Yield (70 mg, 67%) from rac-
2a (0.1 g, 0.3 mmol). 1H NMR (CDCl3) d¼7.63 (d,
J¼6.7 Hz, 1H), 7.36 (d, J¼5.8 Hz, 1H), 6.83 (m, 2H),
6.24 (d, J¼4.7 Hz, 1H), 5.74 (s, 1H), 4.62 (d, J¼3.8 Hz,
2H), 3.39 (m, 2H), 2.12 (m, 3H), 1.76 (s, 3H), 1.63 (s, 3H),
1.28 (s, 3H); 13C NMR (CDCl3) d¼162.2, 155.9, 143.6,
135.5, 128.8, 124.3, 118.8, 113.4, 101.6, 78.2, 73.0, 39.4,
36.8, 29.7, 26.5, 26.0, 23.4, 16.7, 15.9.