-
1
-
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0000664472
-
-
and references therein
-
Petit, G. R. Y.; Williams, M. D.; Boyd, M. M. R. J. Nat. Prod. 1998, 61, 953 and references therein.
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(1998)
J. Nat. Prod.
, vol.61
, pp. 953
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-
Petit, G.R.Y.1
Williams, M.D.2
Boyd, M.M.R.3
-
2
-
-
85037493706
-
-
Epoxide 2a was synthesized from the commercially available steroid, hecogenin in seven steps. The detailed experimental procedure is shown in the Supporting Information
-
Epoxide 2a was synthesized from the commercially available steroid, hecogenin in seven steps. The detailed experimental procedure is shown in the Supporting Information.
-
-
-
-
3
-
-
0040008107
-
-
3SiH, Kotsuki, H.; Datta, P. K.; Hayakawa, H.; Suenaga, H. Synthesis 1995, 1349.
-
(1995)
Synthesis
, pp. 1349
-
-
Kotsuki, H.1
Datta, P.K.2
Hayakawa, H.3
Suenaga, H.4
-
4
-
-
0001314965
-
-
2H, Cacchi, S.; Morera, E.; Ortar, G. Tetrahedron Lett. 1984, 25, 42, 4821.
-
(1984)
Tetrahedron Lett.
, vol.25
, Issue.42
, pp. 4821
-
-
Cacchi, S.1
Morera, E.2
Ortar, G.3
-
5
-
-
85037508128
-
-
3SnH, see ref 7
-
3SnH, see ref 7.
-
-
-
-
6
-
-
0033578622
-
-
3, Lipshutz, B, H,; Buzard, D. J.; Vivian, W. Tetrahedron Lett. 1999, 40, 6871.
-
(1999)
Tetrahedron Lett.
, vol.40
, pp. 6871
-
-
Lipshutz, B.H.1
Buzard, D.J.2
Vivian, W.3
-
7
-
-
85027877554
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-
(a) Comins, D. L.; Dehghani, A.; Foti, C. J.; Joseph, S. P. Org. Synth. 1997, 74, 77.
-
(1997)
Org. Synth.
, vol.74
, pp. 77
-
-
Comins, D.L.1
Dehghani, A.2
Foti, C.J.3
Joseph, S.P.4
-
9
-
-
0000278319
-
-
It was reported that in the case of 1-acetoxy-2-bromo-2-alkenes, the bromo substituent dramatically reduces the reactivity of the olefin in Pd-catalyzed substitutions, and that coupling between bromoalkenes and terminal alkynes proceeds without side reactions with acetoxy substituents. (a) Nwokogu, G. C. Tetrahedron Lett. 1984, 25, 31, 3263.
-
(1984)
Tetrahedron Lett.
, vol.25
, Issue.31
, pp. 3263
-
-
Nwokogu, G.C.1
-
11
-
-
0033531676
-
-
Similarly, it was recently reported that Pd-catalyzed carbonylation of 1-acetoxy-2-bromo-2-alkenes proceeds without involvement of the allylic ester. Trost, B. M.; Oslob, J. D. J. Am. Chem. Soc. 1999, 121, 3057.
-
(1999)
J. Am. Chem. Soc.
, vol.121
, pp. 3057
-
-
Trost, B.M.1
Oslob, J.D.2
-
12
-
-
85037517109
-
-
3b gave a mixture of unidentifiable products, presumably due to acid sensitivity of vinyl epoxide
-
3b gave a mixture of unidentifiable products, presumably due to acid sensitivity of vinyl epoxide.
-
-
-
-
16
-
-
85037499545
-
-
Because of the difficulty in separation from starting material, 4a was not isolated in most cases. An alternative way to make this compound is described in the Supporting Information
-
Because of the difficulty in separation from starting material, 4a was not isolated in most cases. An alternative way to make this compound is described in the Supporting Information.
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-
-
-
17
-
-
0000870026
-
-
(a) Julian, P. L.; Meyer, E. W.; Ryden, I. J. Am. Chem. Soc. 1950, 72, 367.
-
(1950)
J. Am. Chem. Soc.
, vol.72
, pp. 367
-
-
Julian, P.L.1
Meyer, E.W.2
Ryden, I.3
-
19
-
-
0001020134
-
-
(c) Julian, P. L.; Meyer, E. W.; Karpel; W. J.; Waller, I. R. J. Am. Chem. Soc. 1950, 72, 5145.
-
(1950)
J. Am. Chem. Soc.
, vol.72
, pp. 5145
-
-
Julian, P.L.1
Meyer, E.W.2
Karpel, W.J.3
Waller, I.R.4
-
20
-
-
85037514005
-
-
12 although Pd-catalyzed reduction has also been described. In our case, addition of more than 1 equiv of the hydride resulted in a mixture of products resulting from over-reduction of the allyl epoxide, along with 4, 7, and 5. Addition of additional Pd catalyst had no effect on the reaction
-
12 although Pd-catalyzed reduction has also been described. In our case, addition of more than 1 equiv of the hydride resulted in a mixture of products resulting from over-reduction of the allyl epoxide, along with 4, 7, and 5. Addition of additional Pd catalyst had no effect on the reaction.
-
-
-
-
22
-
-
85037519152
-
-
It is speculated that the steric repulsion between C12 TBS group of 14a suppresses its formation, resulting in the lower ratio. (matrix presented)
-
It is speculated that the steric repulsion between C12 TBS group of 14a suppresses its formation, resulting in the lower ratio. (matrix presented)
-
-
-
-
23
-
-
85037514628
-
-
17(20) olefin in steroids is hydrogenated from the α-face, the C17 configuration in 17 is R, as shown (matrix prsented)
-
17(20) olefin in steroids is hydrogenated from the α-face, the C17 configuration in 17 is R, as shown. (matrix prsented)
-
-
-
-
24
-
-
85037515727
-
-
The high regioselectivity in the reduction of 4a compared to 4b can be explained by the relative stability of the isomeric πallyl palladium species in each case. It is likely that 13 is more stable than 12 because of less steric repulsion between the steroidal core. However, sterics between Pd ligand and bulky TBS protecting group at C12 (see 13a) could invert the relative stability. Transmetalation and reductive elimination gives the reduced compounds, of which the ratio should reflect the energy difference between 12 and 13. (matrix presented)
-
The high regioselectivity in the reduction of 4a compared to 4b can be explained by the relative stability of the isomeric πallyl palladium species in each case. It is likely that 13 is more stable than 12 because of less steric repulsion between the steroidal core. However, sterics between Pd ligand and bulky TBS protecting group at C12 (see 13a) could invert the relative stability. Transmetalation and reductive elimination gives the reduced compounds, of which the ratio should reflect the energy difference between 12 and 13. (matrix presented)
-
-
-
-
26
-
-
85037498832
-
-
4. It is assumed that the major isomer is the one with the β-configuration at C16, 7a. (matrix presented)
-
4. It is assumed that the major isomer is the one with the β-configuration at C16, 7a. (matrix presented)
-
-
-
-
27
-
-
85037507264
-
-
3-SnH gave different products depending on substrates
-
3-SnH gave different products depending on substrates.
-
-
-
-
28
-
-
0040601419
-
-
(a) Tanabe, M.; Crowe, D. F.; Dehn, R. L. Tetrahedron Lett. 1967, 40, 3943.
-
(1967)
Tetrahedron Lett.
, vol.40
, pp. 3943
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-
Tanabe, M.1
Crowe, D.F.2
Dehn, R.L.3
-
29
-
-
84987288489
-
-
(b) Muller, R. K.; Felix, D.; Schreiber, J.; Eschenmoser, A. Helv. Chim. Acta 1970, 53, 1479.
-
(1970)
Helv. Chim. Acta
, vol.53
, pp. 1479
-
-
Muller, R.K.1
Felix, D.2
Schreiber, J.3
Eschenmoser, A.4
-
30
-
-
33751386638
-
-
Farina, V.; Krishnan, B.; Marshall, D. R.; Roth, G. P. J. Org. Chem. 1993, 58, 5434.
-
(1993)
J. Org. Chem.
, vol.58
, pp. 5434
-
-
Farina, V.1
Krishnan, B.2
Marshall, D.R.3
Roth, G.P.4
-
31
-
-
85037514562
-
-
8c
-
8c
-
-
-
-
32
-
-
85037503867
-
-
8c
-
8c
-
-
-
-
33
-
-
0001467798
-
-
For β-elimination of Pd-methoxide to form "Pd-H", (a) Grushin, V. V. Chem. Rev. 1996, 96, 2011.
-
(1996)
Chem. Rev.
, vol.96
, pp. 2011
-
-
Grushin, V.V.1
-
35
-
-
0000793426
-
-
(c) Milstein, D.; Frolow, F.; Portnoy, M. Organometallics 1991, 10, 3960.
-
(1991)
Organometallics
, vol.10
, pp. 3960
-
-
Milstein, D.1
Frolow, F.2
Portnoy, M.3
-
37
-
-
85037500594
-
-
23a the corresponding reaction with aldehydes is not precedented
-
23a the corresponding reaction with aldehydes is not precedented.
-
-
-
-
38
-
-
85037503612
-
-
27 We therefore speculate that the intramolecular version of this transformation may be possible
-
27 We therefore speculate that the intramolecular version of this transformation may be possible.
-
-
-
-
39
-
-
37049089453
-
-
A bis-π-allylpalladium species was reported to have a nucleophilic character: (a) Nakamura, H.; Asao, N.; Yamamoto, Y. J. Chem. Soc., Chem. Commun. 1995, 1273.
-
(1995)
J. Chem. Soc., Chem. Commun.
, pp. 1273
-
-
Nakamura, H.1
Asao, N.2
Yamamoto, Y.3
-
40
-
-
0030755285
-
-
(b) Nakamura, H.; Shim, J. G.; Yamamoto, Y. J. Am. Chem. Soc. 1997, 119, 8113.
-
(1997)
J. Am. Chem. Soc.
, vol.119
, pp. 8113
-
-
Nakamura, H.1
Shim, J.G.2
Yamamoto, Y.3
-
42
-
-
85037501642
-
-
3SnH
-
3SnH.
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