-
3
-
-
0034625430
-
-
M.P. Bertrand, S. Coantic, L. Feray, R. Nouguier, and P. Perfetti Tetrahedron 56 2000 3951 3961
-
(2000)
Tetrahedron
, vol.56
, pp. 3951-3961
-
-
Bertrand, M.P.1
Coantic, S.2
Feray, L.3
Nouguier, R.4
Perfetti, P.5
-
4
-
-
0033966817
-
-
For related studies see also: (c) H. Miyabe, C. Ushiro, M. Ueda, K. Yamakawa, and T. Naito J. Org. Chem. 65 2000 176 185
-
(2000)
J. Org. Chem.
, vol.65
, pp. 176-185
-
-
Miyabe, H.1
Ushiro, C.2
Ueda, M.3
Yamakawa, K.4
Naito, T.5
-
8
-
-
0013323218
-
-
K. Yamada, H. Fujihara, Y. Yamamoto, Y. Miwa, T. Taga, and K. Tomioka Org. Lett. 4 2002 3509 3511
-
(2002)
Org. Lett.
, vol.4
, pp. 3509-3511
-
-
Yamada, K.1
Fujihara, H.2
Yamamoto, Y.3
Miwa, Y.4
Taga, T.5
Tomioka, K.6
-
9
-
-
1442299995
-
-
K. Yamada, Y. Yamamoto, Y. Miwa, M. Maekawa, and K. Tomioka J. Org. Chem. 69 2004 1531 1534
-
(2004)
J. Org. Chem.
, vol.69
, pp. 1531-1534
-
-
Yamada, K.1
Yamamoto, Y.2
Miwa, Y.3
Maekawa, M.4
Tomioka, K.5
-
11
-
-
0036979996
-
-
S. Bazin, L. Feray, J.-V. Naubron, D. Siri, and M.P. Bertrand J. Chem. Soc., Chem. Commun. 2002 2506 2507
-
(2002)
J. Chem. Soc., Chem. Commun.
, pp. 2506-2507
-
-
Bazin, S.1
Feray, L.2
Naubron, J.-V.3
Siri, D.4
Bertrand, M.P.5
-
12
-
-
0026084766
-
-
For an example of aldol condensation of zinc enolates derived from N-acyloxazolidinones see: Y. Ito, and S. Terashima Tetrahedron 47 1991 2821 2834
-
(1991)
Tetrahedron
, vol.47
, pp. 2821-2834
-
-
Ito, Y.1
Terashima, S.2
-
18
-
-
0035498332
-
-
For a general review on organoboranes in radical chemistry see: (f) C. Ollivier, and P. Renaud Chem. Rev. 101 2001 3415 3434
-
(2001)
Chem. Rev.
, vol.101
, pp. 3415-3434
-
-
Ollivier, C.1
Renaud, P.2
-
19
-
-
85030798281
-
-
note
-
3B behave differently might be related to the chelating character of diethylzinc which would induce an increase of the spin density at the oxygen atom. Alternatively, homolytic substitution at zinc might have a lower activation energy, allowing the reaction to proceed with radicals having a spin density at oxygen lower than enoxyl radicals.
-
-
-
-
20
-
-
1942496535
-
-
It is worth noting that owing to the fast reaction with oxygen, the fourth ligand of zinc might well be EtOO instead of Et. See: (a) J. Lewinski, Z. Ochal, E. Bojarski, E. Tratkiewicz, I. Justyniak, and J. Lipkowski Angew. Chem., Int. Ed. 42 2003 4643 4646
-
(2003)
Angew. Chem., Int. Ed.
, vol.42
, pp. 4643-4646
-
-
Lewinski, J.1
Ochal, Z.2
Bojarski, E.3
Tratkiewicz, E.4
Justyniak, I.5
Lipkowski, J.6
-
23
-
-
0037155527
-
-
M.P. Sibi, P. Liu, J. Ji, S. Hajra, and J.-X. Chen J. Org. Chem. 67 2002 1738 1745
-
(2002)
J. Org. Chem.
, vol.67
, pp. 1738-1745
-
-
Sibi, M.P.1
Liu, P.2
Ji, J.3
Hajra, S.4
Chen, J.-X.5
-
24
-
-
0032960346
-
-
For a general review on conjugate radical additions see: (a) M. Sibi, and N.A. Porter Acc. Chem. Res. 32 1999 163 171
-
(1999)
Acc. Chem. Res.
, vol.32
, pp. 163-171
-
-
Sibi, M.1
Porter, N.A.2
-
27
-
-
85030802490
-
-
note
-
At lower temperature the reaction was slowed down; it gave lower yields with no significant improvement of the selectivity.
-
-
-
-
28
-
-
85030794292
-
-
note
-
Reactions performed without adding oxygen in an undegassed solvent revealed much slower and gave very poor yields. Under carefully degassed conditions most of the starting material remained unchanged.
-
-
-
-
29
-
-
0003170224
-
-
For general reviews on the synthesis and the reactivity of organozinc see: P. Knochel Synlett 1995 393 403
-
(1995)
Synlett
, pp. 393-403
-
-
Knochel, P.1
-
32
-
-
85030800791
-
-
note
-
According to Table 1, it can be noted that the carbonyl group bearing the auxiliary induces a deshielding of the cis protons. The deshielding effect is significant on H4 (0.20-0.23 ppm (cf. 3, 5 / 7), or 0.40-0.53 ppm (cf 19 / 20 or 15 / 17)), it is negligible on H2. H3 is shielded by 0.34-0.67 ppm by the syn alkyl group (cf. 3, 5 / 4, 6 or 15, 19 / 16, 18), it suffers a larger shielding effect from the syn phenyl group (1.03-1.08 ppm, (cf. 7 / 4, 6) or 0.83-1.11 ppm, (cf. 17, 20 / 16, 18)).
-
-
-
-
35
-
-
85030793536
-
-
note
-
The cleavage of a pure sample of 5, later obtained from substrate 2, confirmed that 5 did not lead to acid 8, but to a mixture of products containing another amide-alcohol 12b.
-
-
-
-
36
-
-
85030793608
-
-
note
-
-.
-
-
-
-
37
-
-
85030800640
-
-
note
-
1H NMR from the integration of the overlapping AB parts of the ABX systems in each diastereomer.
-
-
-
-
38
-
-
85030796804
-
-
note
-
The tridimensional structure of 5 clearly reveals that both faces of the exocyclic carbonyl group are hindered and none can be attacked by the nucleophile.
-
-
-
-
39
-
-
85030802870
-
-
note
-
1H NMR spectrum of the mixture after elimination of unreacted benzaldehyde by liquid chromatography.
-
-
-
-
40
-
-
85030795417
-
-
note
-
1H NMR signals very close to those of 9 (cf. Table 1).
-
-
-
-
41
-
-
85030796650
-
-
note
-
It must be noted that in the NMR spectra of 13h (and 13c) and to a lesser extent the spectrum of 13d, the doublet corresponding to the vinylic proton and the signal of the corresponding carbon are broadened. This phenomenon is probably related to the rate of rotation around the C-N bond. Lowering the temperature at -10 °C afforded well resolved spectra and allowed to unambiguously establish the correlation between the protons and the corresponding carbons by HMQC.
-
-
-
-
42
-
-
85030801560
-
-
note
-
34=11.4 Hz).
-
-
-
-
43
-
-
85030796074
-
-
note
-
1H NMR spectrum of enriched chromatographic fractions clearly show the characteristic signals of the ethoxycarbonyl groups and the absence of the oxazolidinone protons (cf. Section 4.2.20).
-
-
-
-
46
-
-
85030804934
-
-
note
-
Supporting Information content: Chiral HPLC analyses of racemic and optically pure lactones 9 and 22 (S2-S5), of lactones 15, 16, 17, 18, 19 and 20 (S6), detailed chiral HPLC conditions (S7). Significant NOESY correlations for lactones 9 and 15-20 (S8).
-
-
-
-
47
-
-
85030795500
-
-
note
-
Crystallographic data (excluding structure factors) for the structures in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication numbers CCDC 257463 for lactone 3, 257464 for lactone 4, 257465 for lactone 5, and 257466 for lactone 18. Copies of the data can be obtained, free of charge, on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [Fax: +44-(0)1223-336033 or e-mail: deposit@ccdc.cam.ac.uk ].
-
-
-
|