dq, J = 7.3, 1.5, CH -4′), 2.07 (3H, s, CH -2″), 6.01 (1H, qq, J = 7.3, 1.5, CH-3′), three AB systems at 5.34 and 6.61 (1H each,
3
3
d, J = 5.0, H-9 and H-10, respectively), 6.19 and 7.56 (1H each, d, J = 9.6, H-3 and H-4, respectively), and 6.78 and 7.33 (1H,
each, d, J = 8.4, H-6 and H-5, respectively). 13C NMR spectrum (100.61 MHz, δ , ppm): 14.6 C(4′), 19.4 C(5′), 19.7 C(2″),
C
2
1
1.2 and 24.3 gem. (Me) , 59.1 C(10), 6.95 C(9), 77.1 C(8), 106.3 C(10a), 111.5 C(4a), 112.3 C(3), 113.4 C(6), 126.5 C(2′),
28.2 C(5), 136.9 C(3′), 142.2 C(4), 152.8 C(10b), 155.6 C(6a), 158.7 C(2), 165.9 C(1′), 168.8 C(1′′). Mass spectrum (m/z):
found 386.13559, C H O ; calc. (m/z) 386.13654. Mass spectrum (m/z, I , %): 386 (4) [M] , 326 (25), 311 (46), 287 (64),
61 (26), 246 (11), 245 (69), 244 (21), 243 (21), 229 (82), 227 (30). IR spectrum (ν, cm ): 1146, 1191, 1608, 1741 (lactone
2
+
2
1
22
7
rel
−
1
2
C=O), 2856 and 2929. UV spectrum (EtOH, λmax, nm, log ε): 206 (4.38), 256 (3.48), 323 (3.94).
Hydrolysis of (+)-Pteryxin in Basic Medium. A solution of 1 (531 mg, 1.38 mmol) in dioxane (40 mL) was treated
with stirring with KOH solution (80 mL, 0.5 N, 40.0 mmol), heated at 60°C for 2 h, cooled, treated with stirring with H SO
2
4
(
27 mL, 10%) until the pH was 4, and extracted with CHCl (4 × 10 mL). The extract was dried over MgSO . The solvent was
3
4
removed in vacuo to produce an oily residue that, according to analytical TLC (eluent hexane:AcOEt, 1:1 v/v), lacked starting
+)-pteryxin and contained a mixture of angelic acid and cis- and trans-khellactones (R 0.8, 0.6, and 0.5, respectively).
(
f
According to the PMR spectrum, a resonance for protons of the methyl group ofacetic acid (δ 2.1 ppm) was observed in addition
tothe resonances ofthe aforementioned products. This residue was dissolved in CHCl (5 mL) and subjected topreparative TLC
3
on a loose layer of silica gel (60-200 µm) containing K-35 luminophor (1%). We used plates (30 × 30 cm) with a sorbent layer
(
2 mm) and elution by hexane:AcOEt (1:2 v/v). The upper band that absorbed weakly in UV light and contained angelic acid
and the lower band that absorbed strongly in UV light and contained a mixture of cis- and trans-khellactones were collected.
The products were eluted from the sorbents byEtOAc. Solvent was removed from the effluents in vacuo to produce angelic acid
(102 mg, 74%) and a mixture of cis- and trans-khellactones (292 mg, 81%) (the cis/trans ratio according of PMR spectra was
1
:1.3). A solution (50 mg) of the aforementioned lactone mixture in CHCl (0.5 mL) was subjected to preparative TLC on
3
Sorbfil UV 254 plates (10 × 20 cm) with elution by hexane:AcOEt (1:1 v/v) and eluent rise 9 cm. Two bands that absorbed in
UV light with R 0.5 and 0.6 and corresponded to trans- and cis-khellactone, respectively, were collected by elution from the
f
sorbent with EtOAc. Solvent was removed in vacuo to produce the crystalline compounds.
Angelic acid: mp 42-44°C (sublimation at 100°C/1 torr). PMR spectrum (200.13 MHz, CDCl , δ, ppm, J/Hz): 1.88
3
(
3H, quintet, J = 1.4, CH -2), 2.01 (3H, dq, J = 7.4, 1.4, CH -4), 6.20 (1H, qq, J = 7.4, 1.4, H-3), 12.25 (1H, br.s, OH). Lit. [12]
3 3
mp 42-44°C. The PMR spectrum agreed with that published [12].
(
−)-trans-Khellactone: mp 185-186°C (benzene), [α]57820 −18.3° (c 2.4, CHCl ). PMR spectrum (200.13 MHz,
3
CDCl , δ, ppm, J/Hz): 1.29 and 1.50 [3H each, s, gem. (Me) ], three AB systems at 3.83 and 4.98 (1H each, d, J = 6.8, H-9 and
3
2
H-10, respectively), 6.23 and 7.63 (1H each, d, J = 9.6, H-3 and H-4, respectively), and 6.76 and 7.29 (1H each, d, J = 8.6, H-6
and H-5, respectively).
(
+)-cis-Khellactone: mp174-175°C(benzene), [α]57820 +81.2°(c 2.0, CHCl ). PMRspectrum (200.13 MHz, CDCl ,
3 3
δ, ppm, J/Hz): 1.39 and 1.44 [3H each, s, gem. (Me) ], three AB systems at 3.84 and 5.19 (1H each, d, J = 5.2, H-9 and H-10,
2
respectively), 6.23 and 7.64 (1H each, d, J = 9.6, H-3 and H-4, respectively), and 6.77 and 7.30 (1H each, d, J = 8.6, H-6 and
H-5, respectively).
Literature data [17]: (−)-trans-khellactone, mp 185-186°C (benzene), [α]D21 −18.0 ± 1.0° (c 0.90, CHCl3);
(
(
+)-cis-khellactone, mp 174-175°C (benzene), [α]D20 +80.9 ± 1.0° (c 1.04, CHCl3). PMR spectra agreed with those for
+)-trans- and (−)-cis-khellactone, respectively [18].
ACKNOWLEDGMENT
The work was supported financiallybythe Russian Foundation for Basic Research (Grant No. 08-03-90200-Mong_a).
REFERENCES
1
.
I. Yu. Bagryanskaya, Yu. V. Gatilov, S. A. Osadchii, A. A. Martynov, M. M. Shakirov, E. E. Shul′ts, and
G. A. Tolstikov, Khim. Prir. Soedin., 541 (2005).
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80