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HELVETICA CHIMICA ACTA – Vol. 88 (2005)
2.17 (d, J=10.3, HꢀC(9)); 2.20 (s, Me(21)); 2.94 (br. d, J=7.2, HbꢀC(17)); 3.52–3.62 (m, HꢀC(3)); 5.12 (d,
J=10.1, HaꢀC(12)); 5.60 (t, J=10.1, HbꢀC(11)); 7.42 (t, J=7.7, HꢀC(4’,6’)); 7.55 (t, J=7.4, HꢀC(5’)); 7.95
(d, J=7.2, HꢀC(3’,7’)); for sugar resonances, see Table 1. 13C-NMR: see Table 2. HR-ESI-MS: 1015.4309
([M+K]+, C47H68KO1þ4 ; calc. 1015.4305).
Acid Hydrolysis of 1. A soln. of 1 (5 mg) in MeOH (3 ml) and 0.1M H2SO4 (1 ml) was kept at 608 for 30 min.
Then, H2O (3 ml) was added, the mixture was concentrated to a volume of ca. 4 ml, and kept at 608 for another
30 min, before cooled to r.t. The soln. was extracted with Et2O (3×5 ml), the org. layer was washed with H2O
(4×5 ml), dried (Na2SO4), and evaporated to dryness. The resulting residue was recrystallized from PE/
AcOEt. The aq. acidic layer of the hydrolysate was neutralized with 5% aq. Ba(OH)2 soln. The precipitate
was filtered, and the filtrate was evaporated. The residue, pachybiose, was compared with an authentic sample
by paper chromatography (upper layer of BuOH/AcOH/H2O 4 :1 :5) and TLC (CHCl3/MeOH 9 :1).
Data of Tenacigenin A (1a). Colorless amorphous powder. 1H-NMR (500 MHz, CDCl3): 1.15 (s, Me(19));
1.18 (s, Me(21)); 1.22 (s, Me(18)); 1.86 (br. s, HꢀC(17)); 2.43 (br. s, HꢀC(9)); 3.61–3.67 (m, HꢀC(3)); 3.98 (d,
J=2.4, HaꢀC(12)); 4.30 (br. d, J=2.6, HbꢀC(11)). 13C-NMR: see Table 2. ESI-MS: 387.4 ([M+Na]+, C21H32-
NaOþ5 ).
Enzymatic Hydrolysis of 3. A soln. of 0.1M AcOH/AcONa (pH 4.6) buffer (1 ml) and b-glucosidase (30 ml;
250 U/ml; Sigma) was added to 3 (2 mg). The mixture was incubated at 608 for 30 min, and then extracted with
CHCl3 (3×5 ml). The CHCl3 layer was evaporated under reduced pressure, and the residue was identified as
tenacissoside I [8] by TLC comparison with an authentic sample (visualization with CHCl3/MeOH 9 :1). The
aq. layer contained only one monosaccharide identified as glucose by paper chromatography (upper layer of
BuOH/AcOH/H2O 4 :1:5).
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Received April 27, 2005