10.1002/ejoc.201801432
European Journal of Organic Chemistry
FULL PAPER
concentrated. The residue was purified by flash chromatography
to afford compound 19b (37mg, 0.09 mmol, 60%) as white
crystalline solid. Rf (60% hexane - EtOAc) 0.69; [α]D30 = + 6.5 (c
0.34, CHCl3); m.p. = 110-111º C (CH2Cl2/hexane); νmax (KBr)
3491 (OH), 2926, 1448, 1076 cm-1; δH (300 MHz, CDCl3) 7.26 -
(0.2 mL) was added. The solution was extracted with EtOAc (3
mL) and then washed with 1 mL of brine. The combined organic
extracts were dried (Na2SO4) and concentrated. The residue
was purified by flash chromatography to afford 21 (23.4 mg,
0.072 mmoles, 65%) as a yellow oil; Rf (60% hexane- EtOAc)
0.6. [α]D31 = +45.6 (c 0.650, CHCl3); νmax (KBr) 2920, 2850, 1194
(C=S), 1070 cm-1; δH (300 MHz CDCl3) 7.22 - 7.47 (15H, m,
aromatics), 5.96 (1H, dd, 3J2,3 = 5.4 Hz, 3J2,1 = 2.7 Hz, H-2), 5.15
7.43 (15H, m, aromatics), 4.81 (1H, s, H-1), 3.69 (1H, dd, 3J5,4
=
9.2 Hz, 3J4,3 = 3.5 Hz, H-4), 3.58 (1H, m, H-5), 3.44 (1H, dd, 2Jgem
3
= 9.6 Hz, J6,5 = 5.1 Hz, H-6), 3.40 (3H, s, OCH3), 3.24 (2H, m,
H-2, H-6), 3.07 (1H, d, 3J2,3 = 3.5 Hz, H-3), 2.72 (1H, d, J 3.15 Hz, (1H, dd, 3J5,4= 8.8 Hz, 3J4,3 = 6.7 Hz, H-4), 4.92 (1H, d, 3J1,2 = 2.7
3
3
Hz, H-1), 4.46 (1H, dd, J3,4 = 6.7 Hz, J3,2 = 5.4 Hz, H-3), 4.32
OH); δC (75 MHz, CDCl3) 143.3 (C-aromatics), 128.5 (C-
aromatics), 128.0 (C-aromatics), 127.3 (C-aromatics), 95.9 (C-1),
87.6 (C-7), 67.1 (C-5), 65.8 (C-6), 65.5 (C-4), 55.6 (OCH3), 54.9
(C-2), 49.7 (C-3). HRMS (EI, MNa+) MNa+ found 441.16689,
C26H26O5Na+. Calcd 441.16725.
2
3
(1H, m, H-5), 3.52 (1H, dd, Jgem= 10.4 Hz, J6,5 = 2.7 Hz, H-6),
3.49 (3H, s, OCH3), 3.36 (1H, dd, 2Jgem = 10.4 Hz, 3J6,5 = 5.7 Hz,
H-6), 2.60 (3H, s, SCH3); δC (75 MHz CDCl3) 214.8 (C=S),
209.19 (C=S), 143.6 (C-aromatics), 128.7 (C-aromatics), 127.9
(C-aromatics), 127, 1(C-aromatics), 98.9 (C-1), 87.0 (C-7), 83.5
(C-4), 72.1 (C-5), 75.6 (C-2), 66.4 (C-5), 63.4 (C-6), 55.8
(OCH3), 19.4 (SCH3), 49.9 (C-3); HRMS (EI, MNa+) MNa+ found
607.07061, C29H28NaO5S4+ calcd 607.07118.
Synthesis of methyl 2,3-anhydro-α-D-allopyranoside 20a: To
a stirred solution of compound 18 (33 mg, 0.13 mmoles) in
CH2Cl2:i-PrOH 80:20 mixture (3.5 mL) activated NaHSO4.Si2O
(33 mg, dried at 105 ºC for 10 h prior to use) was added at room
temperature. After 48 h, the mixture was filtered through a Celite
bed and the filtrate was concentrated. The residue was purified
by flash chromatography to afford compound 20a as a white
solid (13 mg, 0.07 mmoles, 60 %); δH (300 MHz, CDCl3) 4.91
(1H, d, 3J1,2 = 3.1 Hz, H-1), 3.99 (1H, d, 3J5,4 = 8.8 Hz, H-4), 3.86
Synthesis of xanthate 22: To a solution of compound 20b (15
mg, 0.04 mmoles) in 1 ml of anhydrous THF was added a
suspension of NaH (60% dispersion in mineral oil) (1.7 mg, 0.07
mmoles) in 2 mL of anhydrous THF. The mixture was cooled at
0 ºC and CS2 (6 µL, 0.10 mmoles) was added. After 1 h, CH3I (8
µL, 0.13 mmoles) was added. The mixture was stirred during 2
2
3
2
(1H, dd, Jgem = 11.7 Hz, J6,5 = 3.9 Hz, H-6), 3.80 (1H, dd, Jgem
= 11.7 Hz, 3J6,5 = 3.9 Hz, H-6), 3.60 - 3.70 (1H, m, H-5), 3.57 (1H, more hours and then a solution of NH4Cl (sat) (0.15 mL) was
dd, 3J2,1 = 3.1 Hz, 3J2,3 = 4.2 Hz, H-2), 3.49 (1H, dd, 3J3,2 = 4.2 Hz, added. The solution was extracted with EtOAc (3 mL) and then
4J3,1 = 3.9 Hz, H-3), 3.46 (3H, s, OCH3); δC (75 MHz, CDCl3) 94.6
washed with 0.6 mL of brine. The combined organic extracts
were dried (Na2SO4) and concentrated. The residue was purified
(C-1), 87.6 (C-7), 69.0 (C-5), 65.9 (C-5), 62.2 (C-6), 55.8 (OCH3),
55.6 (C-2), 54.0 (C-3).[41]
by flash chromatography to afford 22 (8 mg, 0.02mmoles, 45%)
32
as a yellow oil; Rf (60% hexane- EtOAc) 0.72; [α]D = +105.2 (c
Synthesis of methyl 2,3-anhidro-6-trityl-α-D-allopyranoside
20b: Compound 20a (13 mg, 0.07 mmoles) was dissolved in 1
mL of anhydrous DMF. Then, TrCl (22 mg, 0.08 mmoles) and
DMAP (0.4 mg, 0.004 mmoles) and finally, 17 µl of Et3N were
added. The mixture was stirred during 12 h. After stirring, it was
poured over a H20: ice mixture, the organic phase was extracted
with CHCl2 and washed with saturated solution of NH4Cl (1 mL)
and water (1 mL) and dried (Na2SO4 anh.). The residue was
purified by flash chromatography to afford compound 20b (10.9
mg, 0.03 mmol, 40%) as white solid. Rf (60% hexane- EtOAc)
0.225, CHCl3); νmax (KBr) 2920, 2848, 1209 (C=S), 1060 cm-1; δH
(300 MHz CDCl3) 7.24 - 7.44 (15H, m, aromatics), 6.10 (1H, dd,
3
3
3J4,5 = 9.9 Hz, J4,3 = 1.7 Hz, H-4), 5.01 (1H, d, J1,2= 3.2 Hz, H-
1), 4.57 (1H, ddd, 3J5,4 = 9.9 Hz, 3J5,6 = 4.7 Hz, 3J5,6 = 1.6 Hz, H-
5), 3.77 (1H, dd, 3J3,2 = 4.1 Hz, 3J3,4 = 1.7 Hz, H-3), 3.58 (1H, dd,
3
3J2,3 = 4.1 Hz, J2,1 = 3.2 Hz, H-2), 3.51 (3H, s, OCH3), 3.27 (1H,
2
3
2
dd, Jgem = 10.5 Hz, J6,5 = 1.6 Hz, H-6), 3.06 (1H, dd, Jgem
=
3
10.5 Hz, J6,5 = 4.7 Hz, H-6), 2.38 (3H, s, SCH3); δC (75 MHz
CDCl3) 143.7 (C-aromatics), 128.7 (C-aromatics), 127.9 (C-
aromatics), 127. 6 (C-aromatics), 126.9 (C-aromatic), 214.9
(C=S), 95.5 (C-1), 86.4 (C-7), 76.6 (C-4), 65.8 (C-5), 62.0 (C-6),
55.7 (OCH3), 55.1 (C-2), 50.8 (C-3), 18.8 (SCH3); HRMS (EI,
MNa+) MNa+ found 531.12728, C28H28O5S2Na+ calcd 531.12704.
Synthesis of episulfide 23a: Compound 6 (70 mg, 0.23
mmoles) was dissolved in 7 mL of anhydrous CH3OH and
anhydrous K2CO3 (47 mg, 0.34 mmoles). The mixture was
stirred during 3 h at room temperature under argon atmosphere.
After completion (according to TLC analysis), the reaction
mixture was filtered over a Celite pad and washed with aliquots
of CH3OH. The combine filtrates were concentrated under
reduced pressure to afford compound 23a (11 mg, 0.07 mmoles,
32
0.69; [α]D = + 34.9 (c 0.38, CHCl3); m.p. = 149-150º C
(CH2Cl2/hexane); νmax (KBr) 3479 (OH), 2920, 1448, 1062 cm-1;
δH 300 MHz, CDCl3) 7.22 - 7.47 (15H, m, aromatics), 4.91 (1H, d,
3J1,2 = 3.2 Hz, H-1), 3.88 (1H, m, H-4), 3.78 (1H, m, H-5), 3.55
3
3
(1H, dd, J2,3 = 4.2 Hz, J2,1 = 3.2 Hz, H-2), 3.49 (3H, s, OCH3),
3.39 (1H, dd, 3J3,2 = 4.2 Hz, 4J3,1 = 1.7 Hz, H-3), 3.32 (2H, m, H-
6, H-6); δC (75 MHz, CDCl3) 143.7 (C-aromatics), 128.7 (C-
aromatics), 127.9 (C-aromatics), 127, 1(C-aromatics), 94.4 (C-1),
87.0 (C-7), 67.9 (C-5), 67.2 (C-4), 64.0 (C-6), 55.6 (OCH3), 55.4
(C-2), 53.8 (C-3). HRMS (EI, MNa+) MNa+ found 441.16776,
C26H26O5Na+. Calcd 441.16725.
Synthesis of cyclic xanthate 21: To a solution of compound
19b (45 mg, 0.11 mmoles) in 2 mL of anhydrous THF was
added a suspension of NaH (60% dispersion in mineral oil) (5.2
mg, 0.22 mmoles) in 3 mL of anhydrous THF. The mixture was
cooled at 0 ºC and CS2 (18 µL, 0.30 mmoles) was added. After 1
h, CH3I (24 µL, 0.38 mmoles) was added. The mixture was
stirred during 2 more hours and then a solution of NH4Cl (sat)
29
30 %) as white solid; Rf (60% hexane- EtOAc) 0.35; [α]D = –
43.75 (c 0.525 , CHCl3); m.p. = 149-150º C (CH2Cl2/ hexane);
ν
max(KBr) 3456 (OH), 2937, 1462, 1338, 1286, 1138, 1105, 1058,
3
910 cm-1; δH (300 MHz CDCl3) 5.22 (1H, d, J1,2 = 3.8 Hz, H-1),
5.03 (1H, dd, 3J5,4 = 6.6 Hz, 3J5,6 = 4.4 Hz, H-5), 4.12 (1H, m, H-
2), 3.92 (1H, d, 2Jgem = 7.0 Hz, H-6endo), 3.84 (1H, t, 3J4,3 =3J4,5
=
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