solution of sodium bicarbonate. The organic layer was separ-
ated and the aqueous layer was extracted with dichloromethane
(20 mL × 3). The combined organic layer was dried (Na2SO4)
and evaporated on a rotary evaporator. The residue thus
obtained on column chromatography yielded β-keto ester 1b as
an oil (1.913 g, 75%), Rf 0.23 (PS–ethyl acetate 7:3); [α]D
Ϫ49.17 (c 0.4, CHCl3); νmax (neat)/cmϪ1 1724 (CO2Et), 1745
(N᎐N); δ (CDCl3; 90 MHz) 1.25 (3H, t, J 7.1 Hz, CH2CH3),
᎐
H
1.34 (3H, s, CH3), 1.50 (3H, s, CH3), 3.80 (3H, s, OCH3), 4.00–
4.20 (2H, m, OCH2CH3), 4.26 (1H, d, J 12.0 Hz, OCH2Ar), 4.43
(1H, d, J 3.8 Hz, 2-H), 4.61 (1H, d, J 4.2 Hz, 3-H), 4.62 (1H, d,
J 12.0 Hz, OCH2Ar), 5.40 (1H, d, J 4.0 Hz, 4-H), 6.12 (1H, d,
J 3.8 Hz, 1-H), 6.85 (2H, d, J 8.6 Hz, ArH), 7.16 (2H, d, J 8.6
Hz, ArH); δC (CDCl3; 22.5 MHz) 13.8, 26.5, 26.9, 54.9, 61.2,
71.5, 75.2, 81.7, 82.7, 83.5, 105.4, 112.2, 113.6, 129.0, 129.4,
159.4, 160.5, 184.9 (Calc. for C20H24N2O8: C, 57.13; H, 5.75.
Found: C, 56.91; H, 6.04%).
(C᎐O); δ (CDCl3; 200 MHz) 1.25 (3H, t, J 6.2 Hz, CH2CH3),
᎐
H
1.32 (3H, s, CH3), 1.45 (3H, s, CH3), 3.52 (1H, d, J 18.0 Hz,
COCH2CO), 3.72 (1H, d, J 18.0 Hz, COCH2CO), 3.80 (3H, s,
OCH3), 4.2 (2H, q, J 6.2 Hz, OCH2CH3), 4.26 (1H, d, J 3.6 Hz,
3-H), 4.40 (1H, d, J 2.0 Hz, OCH2Ph), 4.50 (1H, d, J 12.0 Hz,
OCH2Ph), 4.56 (1H, d, J 3.3 Hz, 2-H), 4.70 (1H, d, J 3.6 Hz,
4-H), 6.05 (1H, d, J 3.3 Hz, 1-H), 6.87 (2H, d, J 8.0 Hz, ArH),
7.20 (2H, d, J 8.0 Hz, ArH); δC (CDCl3; 22.5 MHz) 13.8, 25.9,
26.5, 47.1, 54.8, 60.7, 72.1, 81.8, 83.0, 84.6, 105.7, 112.2, 113.5,
128.5, 129.1, 159.2, 166.6, 200.7 (Calc. for C20H26O8: C, 60.90;
H, 6.64. Found: C, 61.08; H, 6.85%).
Ethyl
3-O-allyl-6-deoxy-6-diazo-1,2-O-isopropylidene-ꢀ-D-
xylo-hept-5-ulofuranuronate 2c. Thick oil; 77% yield; Rf 0.36
(PS–ethyl acetate 7:3); [α]D ϩ8.85 (c 0.76, CHCl3); νmax (neat)/
cmϪ1 1673 (C᎐O), 1713 (C᎐O), 2139 (N᎐N); δ (CDCl3; 90
᎐
᎐
᎐
H
MHz) 1.31 (6H, t, J 7.1 Hz, CH2CH3, CH3), 1.45 (3H, s, CH3),
3.50–4.03 (2H, m, OCH CH᎐CH ), 4.23 (2H, q, J 7.1 Hz,
᎐
2
2
OCH2CH3), 4.37 (1H, d, J 3.7 Hz, 3-H), 4.51 (1H, d, J 3.0 Hz,
2-H), 4.95–5.26 (2H, m, CH ᎐CH), 5.37 (1H, d, J 3.7 Hz,
᎐
2
Ethyl 3-O-allyl-6-deoxy-1,2-O-isopropylidene-ꢀ-D-xylo-hept-5-
ulofuranuronate 1c
4-H), 5.45–5.81 (1H, m, CH ᎐CH), 5.98 (1H, d, J 3.0 Hz,
᎐
2
1-H); δC (CDCl3; 22.5 MHz) 14.0, 26.3, 26.9, 42.5, 61.4,
71.0, 75.3, 82.6, 83.7, 105.3, 112.3, 117.4, 133.4, 160.9, 185.2
(Calc. for C15H20N2O7: C, 52.93; H, 5.92. Found: C, 52.80; H,
6.15%).
The reaction of 3-O-allyl-1,2-O-isopropylidene-α--xylo-pento-
dialdose (1.5 g, 6.58 mmol) and ethyl diazoacetate (1.05 mL,
9.87 mmol) in dry CH2Cl2 (100 mL) at Ϫ10 ЊC for 3 h as per the
procedure for 1b gave β-keto ester 1c as an oil (1.811 g, 88%). Rf
0.39 (PS–ethyl acetate 7:3); [α]D Ϫ61.0 (c 0.4, CHCl3); νmax
Ethyl 3-O-benzyl-6-deoxy-6-diazo-1,2-O-isopropylidene-ꢀ-D-
ribo-hept-5-ulofuranuronate 2d. Thick oil; 88% yield; Rf 0.5 (PS–
ethyl acetate 7:3); [α]D ϩ64.7 (c 0.25, CHCl3); νmax (neat)/cmϪ1
(Nujol)/cmϪ1 1723 (CO Et), 1747 (C᎐O); δ (CDCl3; 300
᎐
2
H
MHz) 1.27 (3H, t, J 7.1 Hz, CH2CH3), 1.33 (3H, s, CH3),
1.47 (3H, s, CH3), 3.55 (1H, d, J 16.8 Hz, COCH2CO), 3.74
(1H, d, J 16.8 Hz, COCH2CO), 3.94 (1H, ddt, J 1.5, 5.7, 12.6
1660 (C᎐O), 1720 (CO Et), 2140 (N᎐N); δH (CDCl3; 300 MHz)
᎐
᎐
2
1.32 (3H, t, J 7.1 Hz, CH2CH3), 1.38 (3H, s, CH3), 1.67 (3H,
s, CH3), 4.22 (1H, dd, J 8.4, 4.4 Hz, 3-H), 4.25–4.33 (2H, m,
OCH2CH3), 4.56 (1H, d, J 12.0 Hz, CH2Ph), 4.60 (1H, d, J 3.4
Hz, 2-H), 4.74 (1H, d, J 12.0 Hz, OCH2Ph), 5.41 (1H, d, J 8.6
Hz, 4-H), 5.81 (1H, d, J 3.4 Hz, 1-H), 7.28–7.39 (5H, m, Ph);
δC (CDCl3; 22.5 MHz) 14.3, 26.8, 27.1, 61.8, 72.7, 78.3, 78.4,
79.6, 104.9, 113.8, 128.0, 128.0, 128.4, 128.6, 137.5, 160.1, 187.7
(Calc. for C19H22N2O7: C, 58.45; H, 5.68. Found: C, 58.18; H,
5.63%).
Hz, OCH CH᎐CH ), 4.05 (1H, ddt, J 1.1, 5.5, 12.6 Hz,
᎐
2
2
CH CH᎐CH ), 4.12–4.30 (3H, m, OCH CH , 3-H), 4.56 (1H,
᎐
2
2
2
3
d, J 3.5 Hz, 2-H), 4.69 (1H, d, J 3.6 Hz, 4-H), 5.18–5.28 (2H,
m, CH ᎐CH), 5.70–5.85 (1H, m, CH ᎐CH), 6.06 (1H, d, J 3.5
᎐
᎐
2
2
Hz, 1-H); δC (CDCl3; 22.5 MHz) 13.8, 26.1, 26.7, 47.1, 60.6,
71.3, 79.2, 83.5, 84.9, 105.9, 112.2, 117.4, 133.4, 166.5, 200.8
(Calc. for C13H22O7: C, 53.78; H, 7.64. Found: C, 53.90; H,
7.86%).
General procedure for the synthesis of ꢀ-diazo-ꢁ-keto esters 2a–d
Ethyl 3,6-anhydro-6-benzyl-1,2-O-isopropylidene-ꢀ-D-gluco-
hept-5-ulofuranuronate 3 and ethyl 3,6-anhydro-5-O-benzyl-1,2-
O-isopropylidene-ꢀ-D-xylo-hept-5-enofuranuronate 4a
To a solution of α-diazo-β-keto ester (1 mmol) in dry aceto-
nitrile (30 mL) were added triethylamine (2 mmol) and meth-
anesulfonyl azide (1.1 mmol). The reaction mixture was stirred
at room temperature for 3 h and quenched with aq. sodium
hydroxide (2 M; 1 mL). The organic layer was separated and the
aqueous layer was extracted with ethyl acetate (20 mL × 3). The
combined organic layer was dried (Na2SO4), and evaporated on
a rotary evaporator to give a thick oil, which on column
chromatography (PS–ethyl acetate 19:1) yielded the α-diazo-β-
keto ester.
A solution of α-diazo β-keto ester 2a (0.150 g, 0.385 mmol) and
Rh2(OAc)4 (0.002 g, 0.002 mmol) in benzene (5 mL) under N2
atmosphere was refluxed for 5 min. On cooling, the reaction
mixture was directly loaded onto a silica gel column and puri-
fied by eluting with PS–ethyl acetate (9.5:0.5) to afford, first,
bicycle 3 as a thick oil (0.066 g, 48%), Rf 0.69 (PS–ethyl acetate
7:3); [α]D ϩ54.0 (c 1.0, CHCl3); νmax (neat)/cmϪ1 1779 (C᎐O),
᎐
1744 (C᎐O); δ (CDCl3; 500 MHz) 1.27 (3H, t, J 6.5 Hz,
᎐
H
CH2CH3), 1.30 (3H, s, CH3), 1.39 (3H, s, CH3), 3.26 (2H, AB
quartet, J 14.0 Hz, CCH2Ph), 4.17–4.24 (4H, m, 3-H, 4-H,
OCH2CH3), 4.87 (1H, d, J 3.5 Hz, 2-H), 5.94 (1H, d, J 3.5 Hz,
1-H), 7.17–7.25 (5H, m, Ph); δC (CDCl3; 125 MHz) 13.9, 26.6,
27.3, 40.6, 62.4, 79.1, 82.7, 85.3, 86.9, 107.7, 113.4, 127.1, 128.4,
130.4, 133.8, 166.9, 202.3 (Calc. for C19H22O7: C, 62.97; H, 6.12.
Found: C, 62.76; H, 6.39%).
Ethyl 3-O-benzyl-6-deoxy-6-diazo-1,2-O-isopropylidene-ꢀ-D-
xylo-hept-5-ulofuranuronate 2a. Thick oil; 77% yield; Rf 0.42
(PS–ethyl acetate 7:3); [α]D ϩ1.6 (c 0.44, CHCl3); νmax (neat)/
cmϪ1 1680 (C᎐O), 1712 (C᎐O), 2141 (N᎐N); δ (CDCl3; 500
MHz) 1.24 (3H, t, J 7.1 Hz, CH2CH3), 1.34 (3H, s, CH3), 1.49
(3H, s, CH3), 4.04–4.20 (2H, m, OCH2CH3), 4.34 (1H, d, J 12.3
Hz, CH2Ph), 4.46 (1H, d, J 3.9 Hz, 3-H), 4.63 (1H, d, J 3.6 Hz,
2-H), 4.68 (1H, d, J 12.3 Hz, OCH2Ph), 5.42 (1H, d, J 3.8 Hz,
4-H), 6.12 (1H, d, J 3.6 Hz, 1-H), 7.22–7.34 (5H, m, Ph);
δC (CDCl3; 22.5 MHz) 14.2, 26.6, 27.2, 61.6, 71.9, 75.8, 81.8,
82.6, 83.6, 105.6, 112.6, 128.1, 128.2, 128.3, 137.0, 160.7, 185.2
(Calc. for C19H22N2O7: C, 58.45; H, 5.68. Found: C, 58.55; H,
5.81%).
᎐
᎐
᎐
H
Further elution gave the isomeric bicycle 4a as a white solid
(0.041 g, 29%), mp 75–77 ЊC; Rf 0.57 (PS–ethyl acetate 7:3);
[α]D ϩ26.81 (c 0.45, CHCl3); νmax (Nujol)/cmϪ1 1714 (C᎐O);
᎐
δH (CDCl3; 300 MHz) 1.33 (3H, t, J 7.1 Hz, CH2CH3), 1.36 (3H,
s, CH3), 1.51 (3H, s, CH3), 4.3 (2H, q, J 7.1 Hz, OCH2CH3),
4.84 (1H, d, J 7.0 Hz, 4-H), 4.85 (1H, d, J 3.0 Hz, 2-H), 5.16
(2H, AB quartet, J 12.1 Hz, OCH2Ph), 5.48 (1H, d, J 7.0 Hz,
3-H), 5.93 (1H, d, J 3.0 Hz, 1-H), 7.31–7.43 (5H, m, Ph);
δC (CDCl3; 75 MHz) 14.3, 26.9, 27.8, 61.2, 73.0, 82.8, 83.9, 85.1,
106.1, 113.7, 127.3, 127.9, 128.2, 128.6, 136.5, 146.4, 160.1
(Calc. for C19H22O7: C, 62.97; H, 6.12. Found: C, 62.59; H,
6.72%).
Ethyl
6-deoxy-6-diazo-1,2-O-isopropylidene-3-O-(4-meth-
oxybenzyl)-ꢀ-D-xylo-hept-5-ulofuranuronate 2b. Thick oil; 86%
yield; Rf 0.19 (PS–ethyl acetate 7:3); [α]D ϩ14.81 (c 0.42,
CHCl3); νmax (neat)/cmϪ1 1713 (CO Et), 1777 (C᎐O), 2142
᎐
2
150
J. Chem. Soc., Perkin Trans. 1, 2000, 147–151