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REPRINTS
698
ROMERO ZALIZ AND VARELA
was purified by column chromatography (2:1 EtOAc-hexane) to afford crystalline
13 (1.12 g, 84%); mp 45–47°C; 1H NMR (200 MHz, CDCl3) ꢇ (anomeric region)
5.38 (d, 0.7 H, J1,2 ꢃ 3.3 Hz, H-1ꢀ), 4.55 (d, 0.3 H, J1,2 ꢃ 7.0 Hz, H-1ꢁ); 13C NMR
(50.3 MHz, CDCl3) ꢇ (ꢀ anomer) 91.0 (C-1), 84.0, 80.0, 76.1, 69.3 (C-2, 3, 4, 5),
61.2, 58.9, 58.2 (CH3O), 50.9 (C-6); ꢁ anomer: 97.5 (C-1), 81.8, 75.2, 73.3, 73.2
(C-2, 3, 4, 5), 61.2, 61.0, 58.5 (CH3O), 50.8 (C-6).
Anal. Calcd for C9H17N3O5: C, 43.71; H, 6.94. Found: C, 43.44; H, 7.01.
6-Azido-6-deoxy-2,3,4-tri-O-methyl-D-galactonic acid (14). To a solu-
tion of 13 (1.06 g, 4.29 mmol) in DMSO (13 mL, 190 mmol) was added acetic an-
hydride (8.7 mL, 97 mmol), and the mixture was stirred at room temperature for 24
h. Upon addition of water (20 mL) an oil was formed, and the water solution was
separated and extracted with CH2Cl2 (4 ꢅ 20 mL). The oil and extracts were com-
bined, washed with water, dried (MgSO4) and concentrated. The residue, which
showed by TLC a main spot having Rf 0.60 (1:1 hexane-EtOAc), was purified by
flash chromatography (2:1 hexane-EtOAc) to afford oily lactone 14 (0.83 g, 78%)
slightly contaminated by a polar product (Rf ꢀ 0); [ꢀ]D ꢉ97° (c 1.3, CHCl3); 1H
NMR (200 MHz, CDCl3) ꢇ 4.24 (ddd, J4,5 ꢃ 1.8, J ꢃ 6.2, J ꢃ 7.8 Hz, H-5), 4.05
(d, 1 H, J2,3 ꢃ 9.5 Hz, H-2), 3.88 (dd, 1 H, J3,4 ꢃ 2.2 Hz, H-4), 3.70, 3.61, 3.54 (3
s, 9 H, CH3O), 3.69–3.45 (m, 3 H, H-3, 6, 6ꢈ); 13C NMR (50.3 MHz, CDCl3) ꢇ
169.1 (C-1), 82.0, 78.8, 77.0, 73.8 (C-2, 3, 4, 5), 61.0, 60.9, 58.6 (CH3O), 50.3
(C-6).
On standing in a chloroform solution with a drop of D2O the lactone was
gradually converted into the polar product, which was identified as the corre-
sponding acid. A mixture enriched in the acid (ꢀ 70%) had [ꢀ]D ꢉ57° (c 0.8,
1
CHCl3); H NMR (200 MHz, CDCl3) of 14 (acid form) ꢇ 4.78 (bs, 1 H, CO2H),
3.98 (d, 1 H, J2,3 ꢃ 2.2 Hz, H-2), 3.93 (ddd, 1 H, J4,5 ꢃ 1.5, J5,6 ꢃ 7.3, J5,6ꢈ ꢃ 5.5
Hz, H-5), 3.81 (dd, 1 H, J3,4 ꢃ 8.8 Hz, H-2), 3.62–3.44 (m, 2 H, H-4, 6), 3.50, 3.47,
3.44 (3 s, 9 H, CH3O), 3.35 (dd, 1 H, J6,6ꢈ ꢃ 12.4 Hz, H-6ꢈ); 13C NMR (50.3 MHz,
CDCl3) ꢇ 174.2 (C-1), 80.8, 79.2, 79.0, 69.8 (C-2, 3, 4, 5), 60.5, 60.2, 58.8 (CH3O),
54.1 (C-6).
Anal. Calcd for C9H17N3O6: C, 41.05; H, 6.52; N, 15.96. Found: C, 41.16;
H, 6.39; N, 15.77.
6-Azido-6-deoxy-2,3,4,5-tetra-O-methyl-D-galactonic acid (16). a)
Starting from 14. Freshly powdered KOH (0.65 g) was added to a solution of 14
(0.47 g, 1.90 mmol) in THF (2 mL). To this suspension was added MeI (0.5 mL),
and the mixture was stirred in the dark for 17 h, then poured into water (10 mL) and
stirred for another 0.5 h. The mixture was extracted with CH2Cl2 (2 ꢅ 30 mL), the
aq phase was acidified (pH 3) with conc aq HCl and extracted with ethyl ether
(3 ꢅ 30 mL). The combined organic extracts were dried (MgSO4) and concen-
trated to a syrup, which was chromatographed (4:1 hexane-EtOAc) to afford oily
16 (0.42 g, 79%); [ꢀ]D ꢆ11° (c. 1.2, CHCl3); 1H NMR (200 MHz, CDCl3) ꢇ 7.43
(bs, CO2H), 4.05 (d, 1 H, J2,3 ꢃ 2.1 Hz, H-2), 3.88 (dd, 1 H, J3,4 ꢃ 9.1 Hz, H-3),