References and Notes
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Procedure for
the Synthesis of 6
To an ice-cooled stirred suspension
of Cp2Zr(H)Cl (5.05 g, 19.6 mmol) in THF (50 mL) under
argon protection was added tert-butyl(but-3-ynyloxy)dimethylsilane
(3.61 g, 19.6 mmol), the mixture was stirred at r.t. for 1 h, and
then cooled to 0 ˚C. To the resulting orange solution was
added aldehyde 7 (2.25g, 9.8 mmol) in THF
(35 mL) followed by ZnBr2 (552 mg, 2.45 mmol, dried under
vacuum for 1 h before use), and the mixture was stirred for 24 h
at r.t. The mixture was diluted with EtOAc (100 mL) and aq potassium
sodium
(+)-tartrate (5.7 g, 19.6 mmol), and stirred
for 10 min. The resulting suspension was filtered off and washed
thoroughly with EtOAc (100 mL). The combined filtrate was transferred into
a separatory funnel and successively washed with H2O and
brine. The aqueous phase was extracted with EtOAc (2 × 200
mL), and the combined organic layers were dried over anhyd Na2SO4.
The mixture was concentrated and purified by silica gel chromatography
to afford 6 (3.625 g, 84%) as
a colorless oil: [α] D
²0 -27.0
(c 1.2, CHCl3). ¹H
NMR (300 MHz, CDCl3): δ = 5.72 (m,
1 H), 5.49 (dd, J = 15.0,
6.0 Hz, 1 H), 4.02 (m, 4 H), 3.61 (t, J = 6.0,
2 H), 2.26 (m, 2 H), 1.48 (s, 15 H), 0.86 (s, 9 H), 0.01 (s, 6 H). ¹³C
NMR (100 MHz, CDCl3): δ = 153.8, 130.6,
128.7, 94.1, 80.7, 73.6, 64.7, 62.7, 61.9, 35.9, 28.2, 28.2, 28.2,
26.3, 25.8, 25.8, 25.8, 24.5, 18.1, -5.4, -5.4.
IR (film): 3454, 2931, 2858, 1699, 1473, 1387, 1255, 1174, 1097,
837, 775 cm-¹. MS (EI): m/z (%) = 415
(0.04)[M+], 100 (64.29), 57
(100.00). HRMS (EI): m/z calcd
for C21H41NSiO5 [M+]:
415.2754; found: 415.2765.
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Donohoe TJ.
Newcombe NJ.
Waring MJ.
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1999,
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Wei CQ.
Jiang XR.
Ding Y.
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1998,
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Danheiser RL.
Chandrasekaran S.
Siret P.
Keck GE.
Gras J.-L.
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Stuttle KAJ.
Tuffin DP.
Ansell MF.
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2000,
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Wu Y.
Zhang H.
Zhao Y.
Zhao J.
Chen J.
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Procedure for
the Synthesis of 11
To a suspension of 3 (40
mg, 0.09 mmol) and CeCl3˙7H2O (52
mg, 0.135 mmol) in MeOH (3 mL) was added NaBH4 (4 mg,
0.1 mmol) at 0 ˚C. The mixture was stirred for 15 min, and
the solvent was removed under reduced pressure. Then, H2O
(3 mL) was added to the residue, which was then extracted with EtOAc
(3 × 6 mL). The organic layer was washed
with H2O (3 mL) and brine (3 mL), dried (Na2SO4), filtered,
and and the solvent was removed under reduced pressure to give the
colorless oil, which was directly dissolved in CH2Cl2 (4
mL), and TFA (2 mL) was added. The mixture was stirred for 4 h at
0 ˚C. Then, the solvent was removed in vacuum to give the
crude product 1, which was dissolved in
pyridine (2 mL) and Ac2O (1 mL) containing a catalytic
amount of DMAP. The mixture was stirred at r.t. for 24 h. The reaction
mixture was diluted with EtOAc (10 mL) and washed with sat. NaHCO3 (10
mL). The aqueous layer was extracted with EtOAc (2 × 20
mL). The combined organic extracts were washed with brine (10 mL),
dried over Na2SO4, and filtered. Concentration
of the filtrate followed by chromatography gave pentaacetate 11 (23 mg, 68% over 3 steps) as
a white solid; mp 91-93 ˚C; [α]D
²0 +20.0
(c 0.075, CHCl3). ¹H
NMR (400 MHz, CDCl3): δ = 2.02 (s,
6 H), 2.06 (s, 3 H), 2.07 (s, 6 H), 4.39 and 4.64 (ABq, J = 13.2 Hz,
2 H), 5.02-5.11 (m, 2 H), 5.36 (br d, J = 6.8
Hz, 1 H), 5.45 (dd, J = 10.0,
6.4 Hz, 1 H), 5.70 (br d, J = 8.4
Hz, 1 H), 5.89 (dd, J = 5.2,
1.2 Hz, 1 H). ¹³C NMR (125 MHz, CDCl3): δ = 20.7, 20.8,
20.8, 20.8, 23.3, 44.9, 62.9, 68.5, 69.0, 71.2, 126.1, 134.3, 169.9,
170.0, 170.2, 170.3, 170.4. IR (film): 3363, 3269, 2924, 2850, 1743,
1649, 1556, 1469, 1371, 1223, 1024 cm-¹.
MS (EI): m/z (%) = 385
(0.67) [M+], 326 (100.00),
223 (57.20), 164 (68.60). HRMS (EI): m/z calcd
for C17H23NO9 [M+]:
385.1373; found: 385.1370.
