Potential Degradable Hydrophilic-Hydrophobic Polyurethanes and Polyureas
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Benzyl 2,3,4-tri-O-benzyl-a-D-xylopyranoside (2b)
This was obtained from 1b as an oil (85% yield), following the procedure
described above for 2a. [a]D þ 598 (c 1.7, dichloromethane); IR (cm21): 3063,
1
3028 (Ph), 1074 (C-O-CH2Ph) 734, 696 (Ph); H NMR (CDCl3, 500 MHz): d
(ppm) 7.32 (m, 20H, 4 Ph), 4.97 (1H, d, CHAHB-O-Ph, JHA,HB ¼ 11.0 Hz), 4.90
(1H, d, CHAHB-O-Ph), 4.79 (1H, d, H-1, J1,2 ¼ 3.6 Hz), 4.78 (1H, d, CHCHD-
O-Ph, JHC,HD ¼ 10.5 Hz), 4.76 (1H, d, CHCHD-O-Ph), 4.71 (1H, d, CHEHF-O-
Ph, JHE,HF ¼ 11.9 Hz), 4.66 (1H, d, CHEHF-O-Ph), 4.58 (1H, d, CHGHI-O-Ph,
JHG,HI ¼ 12.1 Hz), 4.54 (1H, d, CHGHI-O-Ph), 4.00 (dd, 1H, H-3,
J2,3 ¼ 9.6 Hz, J3,4 ¼ 8.0 H,), 3.65 (2H, m, H-5A/5B), 3.60 (1H, m, H-4), 3.48
(1H, dd, H-2); 13C NMR (CDCl3, 50 MHz): d (ppm) 139.01, 138.40, 138.31,
137.23 (4C, Ph), 128.46, 128.42, 128.40, 128.33, 128.25, 127.99, 127.94,
127.86, 127.84, 127.81, 127.78, 127.76, 127.69, 127.60, 127.57, 127.52 (20C,
Ph), 95.45 (C-1), 81.49 (C-3), 79.77 (C-2), 78.20 (C-4), 75.76, 73.54, 73.13,
68.74 (4C, OCH2Ph) 60.21 (C-5); MS (CI): m/z 509 (M-1)þ, 419 (M-CH2Ph)þ,
403 (M-OCH2Ph)þ, 181 (PhCH2CHPh)þ, 91 (PhCH2)þ.
HRMS: Theoretical molecular weight for C33H33O5 (M-1)þ 421.247639,
experimental molecular weight: 421.249118.
2,3,4-Tri-O-benzyl-a,b-L-arabinopyranose (3a)
A solution of 2a (1.68 g, 3.3 mmol) in a mixture of 4 M HCl-acetonitrile
16:10 (13 mL) was heated at 808C for 22 h. The mixture was concentrated to
dryness and extracted with CH2Cl2 (50 mL). The extracts were washed with
aq NaHCO3 satd solution (10 mL ꢀ 3), dried (anhydrous MgSO4), and concen-
trated to dryness. The residue was purified by column chromatography (1:1
tert-butylmethyl ether-hexane, Rf ¼ 0.14) to give the title compound as a
white solid (1.1 g, 80%); m.p. 84.1–84.88; [a]D þ 69 (c 0.99, dichloromethane);
1
IR (cm21): 3364 (OH), 3032 (Ph), 1098 (C-O-CH2Ph) 741, 697 (Ph); H NMR
(CDCl3, 500 MHz): d (ppm) a,b anomers in 43:56 ratio; 7.31 (m, 30H, 3 Ph, a
and b anomers), 5.17 (dd, 1H, H-1b, J1,2 ¼ 2.0 Hz, J1,OH ¼ 5.2 Hz,), 4.87 (dd,
1H, H-1a, J1,2 ¼ 10.0 Hz, J1,OH ¼ 2.1 Hz,), 4.80–4.52 (m, 12H, 3 CH2Ph,
a and b anomers), 4.04 (1H, dd, H-5Ab, J4,5A ¼ 8.7 Hz, J5A,5B ¼ 11.4 Hz),
3.92–3.76 (7H, m, H-2b/3a/3b/4a/4b/5Aa/5Ba), 3.67–3.63 (2H, m, H-5Bb/
2a), 3.06 (1H, d, OHb); 13C NMR (CDCl3, 125 MHz): d (ppm) 138.40, 138.21,
138.12, 137.88, 137.69, 137.45 (6C, Ph, a and b anomers), 128.52, 128.47,
128.45, 128.39, 128.06, 128.00, 127.96, 127.93, 127.82, 127.78, 127.69, 127.65
(30C, Ph a and b anomers), 93.46 (C-1a), 92.09 (C-1b), 76.76 (C-2b), 76.20
(C-2a), 76.09 (C-3a), 75.43 (C-3b), 73.81, 73.62 (2C, OCH2Ph, a and/or b
anomers), 73.01 (C-4a), 72.83, 72.70 (2C, OCH2Ph, a and/or b anomers),
72.09 (C-4b), 61.00 (C-5b), 58.24 (C-5a); MS (CI): m/z 403 (M-OH)þ, 329
(M-CH2Ph)þ, 253 (M-CH2Ph-Ph þ H)þ, 181 (PhCH2CHPh)þ, 107 (PhCH2O)þ,