References and Notes
<A NAME="RG21109ST-1">1 </A> See, for example:
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<A NAME="RG21109ST-2">2 </A> For a review, see:
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<A NAME="RG21109ST-6">6 </A> Recently, the C2 stereocenter of
AM2 was also proposed to be 2R by chemical
correlation on a model structure, see:
Kommana P.
Chung SW.
Donaldson WA.
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<A NAME="RG21109ST-11">11 </A> The allyltitanium complex (S,S )-I was prepared
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Hafner A.
Duthaler RO.
Marti R.
Rihs G.
Rothe-Streit P.
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<A NAME="RG21109ST-14">14 </A>
Compound 8 was
prepared from 3-bromopropan-1-ol in 3 steps (40% yield).
<A NAME="RG21109ST-15">15 </A>
The starting aldehyde 11 (20%)
was recovered as the corresponding alcohol after the reductive workup
and no improvement in conversion was observed when the phosphonium
bromide was utilized.
<A NAME="RG21109ST-16">16 </A>
On large scale, longer reaction times
of up to one week and vigorous stirring were required.
<A NAME="RG21109ST-17A">17a </A>
Oikawa H.
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<A NAME="RG21109ST-18">18 </A>
NMR study (see ref. 17 for literature
data): A syn relationship between the
substituents at C23 and C24 was observed for compound 15 (Figure
[¹ ]
).
Figure 1
<A NAME="RG21109ST-19">19 </A>
Other Raney nickel were less selective
and both the benzyl and p -methoxybenzyl
groups were cleaved.
<A NAME="RG21109ST-20">20 </A>
Compound 16 (Mixture
of Epimers at C30)
Colourless oil; [α]D
²0 -49.3
(c 0.5, CHCl3 ). IR (film):
2927, 2855, 1712, 1608, 1513, 1462, 1378, 1248, 1217, 1169, 1094,
1062, 1039, 1006 cm-¹ . ¹ H
NMR (400 MHz, C6 D6 ): δ = 7.19-7.13
(m, 2 H), 6.79-6.74 (m, 2 H), 4.40-4.27 (m, 2 H),
3.96-3.86 (m, 2 H), 3.70 (s, 3 H), 3.69-3.60 (m,
3 H), 3.57-3.46 (m, 2 H), 3.40-3.31 (m, 1 H),
1.89-1.79 (m, 1 H), 1.78-1.68 (m, 2 H), 1.66-1.55
(m, 1 H), 1.54-1.31 (m, 4 H), 1.38 (s, 3 H), 1.30-1.01
(m, 7 H), 1.24 (s, 3 H), 0.96-0.89 (m, 3 H), 0.86-0.71
(m, 27 H), 0.02 to -0.07 (m, 18 H).
¹³ C
NMR (100 MHz, C6 D6 ): δ = 159.1
(s), 130.9 (s), 129.5 and 129.1 (d), 113.7 (d), 107.7 and 107.5
(s), 82.9 (d), 75.1 (d), 75.1 and 74.9 (d), 72.5 and 72.3 (d), 71.6
(d), 69.8 and 69.7 (t), 68.8 and 68.7 (d), 60.6 and 60.4 (t), 55.2
(q), 36.5 and 36.1 (t), 34.2 (t), 33.5 and 33.5 and 33.5 (t), 31.0
(t), 30.7 and 30.6 (t), 29.7 (t), 28.7 and 28.7 (q), 28.5 and 28.4
(d), 26.1 (2C, q), 26.1-25.8 (q), 22.6 and 22.6 (t), 19.8
and 19.8 (q), 18.0-17.9 (s), 16.5 (q), -4.1 to -4.7
(q). ESI-HRMS: m/z calcd for
C44 H86 O8 Si3 + Na+ :
849.5523; found: 849.5506.