F. Sarabia et al. / Tetrahedron 57 ,2001) 10271±10279
10277
3.77±3.70 *m, 4H), 2.65 *ddd, 1H, J13.5, 4.2, 2.3 Hz,
CH2CH*O)CO2Et), 2.00 *ddd, 1H, J13.5, 10.6, 6.6 Hz,
CH2CH*O)CO2Et), 1.29 *t, 3H, J7.1 Hz, CO2CH2CH3);
13C NMR *50.3 MHz, CDCl3) d 171.3, 128.9, 128.5,
128.4, 128.2, 127.7, 127.6, 126.0, 101.3, 83.3, 73.5, 73.1,
72.9, 68.8, 68.0, 52.5, 32.4, 13.8; FAB HRMS *NBA) m/e
399.1815, M11 calcd for C23H26O6: 399.1807.
NMR *50.3 MHz, CDCl3) d 168.3, 135.9, 130.3, 128.2,
128.1, 109.7, 83.4, 76.9, 73.2, 64.9, 61.8, 46.3, 29.8, 26.9,
26.7, 26.1, 19.7, 14.6; FAB HRMS *NBA) m/e 585.2635,
M11 calcd for C30H40N2O8Si: 585.2632.
4.1.10. b-Acetoxy-a-diazo ester 15: acetylation of 14.
b-Acetoxy-a-diazo ester 15 was prepared from hydroxy
diazo 14 *3.0 g, 5.14 mmol) by treatment with acetic anhy-
dride according to the same procedure described above for
the preparation of 5, to obtain pure diazo ester 15 *3.16 g,
98%) as a yellow oil *1:1 mixture of stereoisomers at C-3):
Rf0.82 *silica gel, 25% EtOAc in hexanes); IR *thin ®lm)
nmax *cm21) 2986, 2116, 1754, 1735, 1685, 1667, 1458,
Compound 11b: Rf0.61 *silica gel, 50% EtOAc in
hexanes); IR *thin ®lm) nmax *cm21) 2959, 2875, 1718,
1680, 1487, 1453, 1018; H NMR *400 MHz, CDCl3) d
1
7.49±7.46 *m, 2H, Ph), 7.40±7.30 *m, 8H, Ph), 5.61 *s,
1H, CHPh), 4.73 *d, 1H, J11.7 Hz, PhCH2O), 4.62 *dd,
1H, J5.6, 2.9 Hz), 4.55 *d, 1H, J11.7 Hz, PhCH2O), 4.25
*q, 2H, J7.0 Hz, CO2CH2CH3), 3.91 *dd, 1H, J10.5,
5.5 Hz), 3.75±3.69 *m, 2H), 3.60 *dd, 1H, J9.0, 8.5 Hz),
2.63 *ddd, 1H, J13.0, 4.2, 2.5 Hz, CH2CH*O)CO2Et), 1.86
*ddd, 1H, J13.0, 9.0, 6.7 Hz, CH2CH*O)CO2Et), 1.31 *t,
3H, J7.0 Hz, CO2CH2CH3).
1
1376, 1216; H NMR *400 MHz, CDCl3) d 7.57±7.54 *m,
4H, SiPh2), 7.33±7.25 *m, 6H, SiPh2), 5.78 *d, J2.8 Hz,
0.5H, CH*OAc)CN2), 5.66 *d, J3.5 Hz, 0.5H,
CH*OAc)CN2), 4.96 *ddd, J8.0, 5.0, 2.9 Hz, 0.5H,
CH*OAc)), 4.89 *ddd, J7.8, 4.3, 3.0 Hz, 0.5H,
CH*OAc)), 4.19 *dd, J6.9, 3.5 Hz, 0.5H, CH*OR)),
4.15±4.09 *m, 3H, both isomers), 3.94 *dd, J8.2, 8.1 Hz,
0.5H, CH*OR)), 3.84±3.77 *m, 2H, both isomers), 2.07 *s,
1.5H, OCOCH3), 2.02 *s, 1.5H, OCOCH3), 2.00 *s, 3H,
OCOCH3, both isomers), 1.35 *s, 1.5H, C*CH3)2), 1.32 *s,
1.5H, C*CH3)2), 1.26 *s, 1.5H, C*CH3)2), 1.25 *s, 1.5H,
C*CH3)2), 1.17 *t, J7.5 Hz, 1.5H, CO2CH2CH3), 1.15 *t,
J7.0 Hz, 1.5H, CO2CH2CH3), 0.94 *s, 9H, SiC*CH3)3,
both isomers); 13C NMR *50.3 MHz, CDCl3) *both isomers)
d 171.0, 169.9, 169.4, 135.6, 135.5, 133.2, 129.7, 127.6,
111.1, 110.7, 80.8, 80.1, 75.2, 74.5, 74.4, 73.8, 68.6, 66.6,
63.3, 62.6, 61.1, 27.4, 26.8, 26.6, 25.9, 20.9, 20.8, 20.6,
19.2, 19.1, 14.4, 14.3; FAB HRMS *NBA) m/e 627.2981,
M11 calcd for C32H42N2O9Si: 627.2989.
Compound 12: Rf0.41 *silica gel, 50% EtOAc in hexanes);
IR *thin ®lm) nmax *cm21) 2987, 2881, 1735, 1678, 1487,
1212, 917; H NMR *400 MHz, CDCl3) d 7.53±7.47 *m,
1
2H, Ph), 7.40±7.28 *m, 8H, Ph), 5.56 *s, 1H, CHPh), 5.09 *d,
1H, J8.5 Hz, PhCH), 4.74 *ddd, 1H, J8.5, 5.9, 2.8 Hz,
CHCO2Et), 4.34 *dd, 1H, J10.6, 5.3 Hz, CH2*OCHPh)),
4.26±4.19 *m, 1H, CH*OH)), 4.17 *q, 2H, J7.5 Hz,
CO2CH2CH3), 3.74 *dd, 1H, J9.0, 2.7 Hz, CH*OCHPh)),
3.67 *dd, 1H, J10.4, 10.3 Hz, CH2*OCHPh)), 3.07 *c, 1H,
J8.5 Hz, CH*O)CH2), 2.54 *ddd, 1H, J12.8, 8.9, 5.9 Hz,
CH2CHCO2Et), 2.45 *ddd, 1H, J12.8, 8.2 Hz,
CH2CHCO2Et), 1.70 *bs, 1H, OH), 1.23 *t, 3H, J7.5 Hz,
CO2CH2CH3); 13C NMR *50.3 MHz, CDCl3) d 172.9,
140.4, 137.7, 129.4, 129.0, 128.6, 128.4, 128.3, 128.1,
126.5, 126.2, 101.5, 84.2, 81.8, 76.8, 70.9, 61.8, 60.9,
31.5, 14.1; FAB HRMS *NBA) m/e 399.1797, M11 calcd
for C23H26O6: 399.1807.
4.1.11. Enol ester 16: treatment of b-acetoxy-a-diazo
ester 15 with Rh2ꢀOAc)4. The conversion of 15 *1.10 g,
1.76 mmol) to the enol ester 16 *1.03 g, 98%) was carried
out by treatment with a catalytic amount of Rh2*OAc)4
under similar conditions than for 5: *1:1 mixture of Z/E
isomers): Rf0.78 *silica gel, 25% EtOAc in hexanes); IR
*thin ®lm) nmax *cm21) 3072, 2956, 2864, 1775, 1738, 1665,
1450, 1378, 1016; 1H NMR *400 MHz, CDCl3) d 7.60±7.57
*m, 4H, SiPh2), 7.35±7.26 *m, 6H, SiPh2), 6.34 *d, J
8.8 Hz, 0.5H, CHv*OAc)), 5.78 *d, J9.9 Hz, 0.5H,
CHv*OAc)), 5.24 *dd, 0.5H, J9.9, 8.0 Hz, 0.5H,
CH*OR)CHv*OAc)), 5.08±5.04 *m, 1H, CH*OAc), both
isomers), 4.57 *dd, J8.8, 7.6 Hz, 0.5H, CH*OR)CH-
v*OAc)), 4.21±4.12 *m, 2H), 4.04±3.99 *m, 1H), 3.83±
3.74 *m, 2H), 2.13 *s, 1.5H, CHv*OCOCH3)), 2.12 *s,
1.5H, CHv*OCOCH3)), 1.97 *s, 1.5H, OCOCH3), 1.95 *s,
1.5H, OCOCH3), 1.34 *s, 1.5H, C*CH3)2), 1.33 *s, 1.5H,
C*CH3)2), 1.30 *s, 3H, C*CH3)2), 1.22 *t, J7.5 Hz, 1.5H,
CO2CH2CH3), 1.19 *t, J7.0 Hz, 1.5H, CO2CH2CH3), 0.96
*s, 9H, SiC*CH3)3); 13C NMR *50.3 MHz, CDCl3) *both
isomers) d 170.4, 170.2, 168.9, 168.2, 161.2, 160.9,
140.7, 135.5, 133.2, 129.6, 127.6, 126.2, 110.4, 109.9,
78.0, 77.8, 74.2, 73.9, 73.7, 73.5, 73.3, 27.3, 26.8, 25.9,
20.9, 20.7, 20.3, 20.1, 19.2, 19.1, 14.0, 13.9; FAB HRMS
*NBA) m/e 599.2674, M11 calcd for C32H42O9Si: 599.2676.
4.1.9. b-Hydroxy-a-diazo ester 14: reaction of aldehyde
13 with ethyl diazoacetate. The reaction of aldehyde 1317
*6.2 g, 13.2 mmol, 1.0 equiv.) with ethyl diazoacetate *2.1 g,
19.8 mmol, 1.5 equiv.) mediated by Et2Zn *19.8 mL,
19.8 mmol, 1.5 equiv.), was carried outexactly as described
for 4 above and yielded b-hydroxy-a-diazo ester 14 *6.17 g,
80%) as a 1:1 mixture of stereoisomers at C-3 which was
separated by ¯ash column chromatography on silica gel:
*more polar isomer) Rf0.75 *silica gel, 25% EtOAc in
hexanes); IR *thin ®lm) nmax *cm21) 3430, 3050, 2957,
1
2865, 2109, 1737, 1653, 1390, 1256; H NMR *400 MHz,
CDCl3) d 7.65±7.50 *m, 4H, SiPh2), 7.45±7.30 *m, 6H,
SiPh2), 4.66 *d, J4.5 Hz, 1H, CH*OH)CN2), 4.20±4.05
*m, 4H), 3.83±3.77 *m, 2H), 3.72 *dd, J6.0, 3.5 Hz, 1H),
3.60 *bs, 1H, OH), 3.05 *bs, 1H, OH), 1.30 *s, 3H, C*CH3)2),
1.24 *s, 3H, C*CH3)2), 1.19 *t, J7.5 Hz, 3H, CO2CH2CH3),
0.99 *s, 9H, SiC*CH3)3); 13C NMR *50.3 MHz, CDCl3) d
167.3, 135.4, 129.8, 127.6, 109.8, 81.6, 78.2, 72.9, 67.9,
65.8, 64.8, 60.8, 29.7, 26.7, 25.4, 19.1, 14.3; *less polar
isomer): 7.71±7.62 *m, 4H, SiPh2), 7.38±7.28 *m, 6H,
SiPh2), 4.51 *d, J6.3 Hz, 1H, CH*OH)CN2), 4.25±4.14
*m, 2H), 4.12 *c, J7.5 Hz, 2H, CO2CH2CH3), 3.80±3.71
*m, 3H), 3.65 *bs, 1H, OH), 2.81 *d, J3.8 Hz, 1H, OH),
1.32 *s, 3H, C*CH3)2), 1.28 *s, 3H, C*CH3)2), 1.18 *t, J
7.5 Hz, 3H, CO2CH2CH3), 0.98 *s, 9H, SiC*CH3)3); 13C
4.1.12. Hydrazone 17: reaction of enol ester 16 with
hydrazine. Enol ester 16 *402 mg, 0.67 mmol, 1.0 equiv.)
was reacted with NH2NH2 according to the same procedure
as described above for 6 to afford, after similar processing,