Asymmetric syntheses of new functionalized β-amino alcohols via diastereoselective addition of organometallic reagents onto oxazolidines

Article abstract of DOI:10.1021/jo010779a

Diastereoselective reactions between (S)-phenylglycinol-derived oxazolidines and two unsaturated organolithium reagents afforded chiral β-amino alcohols having vinyl and alkynylsilane moieties. When the same reactions were performed in the presence of titanium isopropoxide, a dramatic change of regioselectivity was observed, from the α- to the γ-position, thus producing β-amino alcohols with allyl or allenylsilane functions. A rationalization of the observed diastereoselectivity was suggested for each case.

Full text of DOI:10.1021/jo010779a

1496
J . Org. Chem. 2002, 67, 1496-1500
Asym m etr ic Syn th eses of New F u n ction a lized â-Am in o Alcoh ols
via Dia ster eoselective Ad d ition of Or ga n om eta llic Rea gen ts on to
Oxa zolid in es
Claude Agami, Se´bastien Comesse, and Catherine Kadouri-Puchot*
Laboratoire de Synthe`se Asyme´trique (UMR CNRS 7611), Case courrier 47,
Universite´ Pierre et Marie Curie, 4 place J ussieu, 75005 Paris, France
kadouri@ccr.jussieu.fr
Received August 1, 2001
Diastereoselective reactions between (S)-phenylglycinol-derived oxazolidines and two unsaturated
organolithium reagents afforded chiral â-amino alcohols having vinyl and alkynylsilane moieties.
When the same reactions were performed in the presence of titanium isopropoxide, a dramatic
change of regioselectivity was observed, from the R- to the γ-position, thus producing â-amino
alcohols with allyl or allenylsilane functions. A rationalization of the observed diastereoselectivity
was suggested for each case.
Diastereoselective additions of Grignard reagents to
derived from propynyltrimethylsilane 4 reacts with com-
pound 1 to afford â-amino alcohols 5 a -e with an alkynyl
appendage (Scheme 1).
Oxazolidines with various R substituents were reacted
with the lithium derivatives 2 and 4, and the results are
listed in Table 1. Yields are substantially lowered in the
case of R ) Me, and the corresponding diastereoisomeric
ratios have not been determined. In all cases, the major
isomer shows the absolute configuration for the carbon
bearing the R-group indicated in Scheme 1.
As shown in Table 2, which shows data for experiments
performed on oxazolidines 1a (R ) Ph), anion 2 was best
generated with 5 equiv of sec-BuLi containing an equimo-
lar amount of tetramethylethylenediamine at -78 °C in
THF (entry 2). As regards medium effects, the beneficial
influence of TMEDA can be ascribed to the fact that it
favors the existence of unaggregated lithium species.6
A change of regioselectivity was found when the above
reactions were performed in the presence of titanium
isopropoxide.7 In this case, addition of Ti(O-i-Pr)4 onto
the organolithium reagents 2 and 4 transforms these
species into covalent allyl or propargyl titanium deriva-
tives 6 and 7, respectively (Scheme 2).
imines or oxazolidines derived from â-amino alcohols are
well documented,1 but works related to similar reactions
with organolithium derivatives are scarcer. Pioneering
works in this field2 have been concerned with the dias-
tereoselective addition of alkyl or aryllithium reagents
onto oxazolidines derived from amino alcohol and espe-
cially from phenylglycinol. As part of a program aimed
at emphasizing the efficiency of asymmetric syntheses
of pipecolic acid derivatives from functionalized â-amino
alcohols,3 we have recently explored4 the reactions be-
tween unsaturated organolithium reagents and oxazo-
lidines 1.
Resu lts
Condensation of (S)-phenylglycinol and various alde-
hydes quantitatively afforded oxazolidines 1a -f. We
observed that reaction of the allyltrimethylsilane-derived
lithium reagent5 2 with these oxazolidines gave â-amino
alcohols 3 a -f, whose vinylsilane moiety showed an
E-geometry. In the same way, the lithiated anion2g
The action of these organometallic compounds onto
oxazolidines 1 thus produces compounds 8 and 9, as
described in Scheme 3.
The use of the titanium derivative 6 gives rise to the
formation of â-amino alcohols possessing an allylsilane
function. Thus, substrates 1c and 1e (R ) Et and i-Pr)
reacted with this reagent and afforded allylsilanes 8c
(50% yield, dr ) 95/5) and 8e (48% yield, dr ) 77/23),
* Corresponding author. Fax: (33) 01 44 27 26 20.
(1) (a) Block, R. Chem. Rev. 1998, 98, 1407. (b) Enders, D.; Reinhold,
U. Tetrahedron: Asymmetry 1997, 8, 1895. For more recent examples,
see: (c) Steinig, A. G.; Spero, D. M. J . Org. Chem. 1999, 64, 2406. (d)
Carillo, L.; Bad`ıa, D.; Dom´ınguez, E.; Anakabe, E.; Osante, I.; Tellitu,
I.; Vicario, J . L. J . Org. Chem. 1999, 64, 1115. (e) Poerwono, H.;
Higashiyama, K.; Yamauchi, T.; Kubo, H.; Ohmiya, S.; Takahashi, H.
Tetrahedron 1998, 54, 13995. (f) Poerwono, H.; Higashiyama, K.;
Takahashi, H. Heterocycles 1998, 47, 263. (g) Barbier, D.; Marazano,
C.; Riche, C.; Das, B. C.; Potier, P. J . Org. Chem. 1998, 63, 1767.
(2) (a) Higashiyama, K.; Inoue, H.; Takahashi, H. Tetrahedron Lett.
1992, 33, 235. (b) Wu, M.-J .; Pridgen, L. N. J . Org. Chem. 1991, 56,
1340. (c) Pridgen, L. N.; Mokhallalati, M. K.; Wu, M.-J . J . Org. Chem.
1992, 57, 1237. (d) Delorme, D.; Berthelette, C.; Lavoie, R.; Roberts,
E. Tetrahedron: Asymmetry 1998, 9, 3963. (e) Higashiyama, K.; Inoue,
H.; Yamauchi, T.; Takahashi, H. J . Chem. Soc., Perkin Trans. 1 1995,
111. (f) Ishii, A.; Miyamoto, F.; Higashiyama, K.; Mikami, K. Tetra-
hedron Lett. 1998, 39, 1199. (g) Hashimoto, Y.; Takaoki, K.; Sudo, A.;
Ogasawara, T.; Saigo, K. Chem. Lett. 1995, 235. (h) Taniyama, D.;
Hasegawa, M.; Tomioka, K. Tetrahedron: Asymmetry 1999, 10, 221.
(3) (a) Agami, C.; Comesse, S.; Kadouri-Puchot, C. J . Org. Chem.
2000, 65, 4435. (b) Agami, C.; Comesse, S.; Kadouri-Puchot, C.;
Lusinchi, M. Synlett 1999, 1094.
(5) (a) Corriu, R. J . P.; Masse, J .; Samate, D. J . Organomet. Chem.
1975, 93, 71. (b) Corriu, R. J . P.; Guerin, C.; M′Boula, J . Tetrahedron
Lett. 1981, 22, 2985. (c) Ayalon-Chass, D.; Ehlinger, E.; Magnus, P. J .
Chem. Soc., Chem. Commun. 1977, 772. (d) Ehlinger, E.; Magnus, P.
Tetrahedron Lett. 1980, 11. (e) Ehlinger, E.; Magnus, P. J . Am. Chem.
Soc. 1980, 102, 5004. (f) Amouroux, R.; Chan, T. H. Tetrahedron Lett.
1978, 4453. (g) Lau, P. W. K.; Chan, T. H. Tetrahedron Lett. 1978,
2383.
(6) Collum, D. B. Acc. Chem. Res. 1993, 26, 227.
(7) (a) Reetz, M. T.; Steinbach, R.; Westermann, J .; Peter, R.;
Wenderoth, B. Chem. Ber. 1985, 118, 1441. (b) Pohnert, G.; Boland,
W. Tetrahedron 1994, 50, 10235. (c) Pohnert, G.; Boland, W. Tetrahe-
dron 1997, 53, 13681.
(4) Agami, C.; Comesse, S.; Kadouri-Puchot, C. Tetrahedron Lett.
2000, 41, 6059.
10.1021/jo010779a CCC: $22.00 © 2002 American Chemical Society
Published on Web 02/08/2002

New Functionalized â-Amino Alcohols
J . Org. Chem., Vol. 67, No. 5, 2002 1497
Sch em e 1
Sch em e 4
Reaction conditions: (a) 6, 50%; (b) (CCl3O)2CO, 6 N NaOH,
CH2Cl2, 53%.
Sch em e 5
Ta ble 1. Rea ction betw een Oxa zolid in es 1 w ith
Or ga n olith iu m Rea gen ts 2a a n d 4b
entry
product
R
yield (%)
dr(c)
92/8
1
2
3
4
5
6
7
8
9
3a
3b
3c
3d
3e
3f
5a
5b
5c
5d
5e
Ph
Me
Et
81
26
45
46
75
80
70
17
55
55
68
80/20
80/20
90/10
95/5
Reaction conditions: (a) 6, 48%; (b) Boc2O, DMAP, AcOEt, 42%
(for 11) and 46% (for 12).
Pr
i-Pr
t-Bu
Ph
Me
Et
Ta ble 3. Dia ster eoselective Ad d ition of Or ga n otita n iu m
Der iva tive 7 on to Oxa zolid in e 1
80/20
90/10
90/10
95/5
diastereoisomeric
10
11
Pr
i-Pr
product
R
yield (%)
ratio
9a
9c
9e
Ph
Et
i-Pr
78
70
55
>95/5
90/10
90/10
a
(CH3)3SiCH2CHdCH2 (5 equiv), sec-BuLi (5 equiv), TMEDA
(5 equiv). b (CH3)3SiCdCCH3 (5 equiv), sec-BuLi (5 equiv), TMEDA
(5 equiv). c Diastereoisomeric ratios were determined by 1H NMR
analysis of the crude mixture.
Sch em e 6
Ta ble 2. Dia ster eoselective Ad d ition of th e Lith iu m
Der iva tive 2 on Com p ou n d 1a (R ) P h )
entry
solvent
additive
yield of 3a (%)
dr of 3a f
1
2
3
4
5
6
THF
THF
THF
THF
THF
Et2O
TMEDAa
TMEDAb
HMPAc
noned
60
81
62
72
73
59
90/10
92/8
56/44
84/16
84/16
72/28
Reaction conditions: (a) H2, Pd/C, abs EtOH, 2 h, 57% from 3c
and 67% from 5c; (b) n-Bu4NF, THF, 1 h; (c) H2, Pd/C, abs EtOH,
40 min, 89% from 5c and 56% from 8c; (d) (CCl3O)2CO, 6 N NaOH,
CH2Cl2, 53%.
PMDTAe
TMEDAb
a
b
sec-BuLi (2.5 equiv), TMEDA (2.5 equiv). sec-BuLi (5 equiv),
TMEDA (5 equiv). c sec-BuLi (2.5 equiv), HMPA/THF (10% v/v).
alcohol 8e was treated with Boc2O in the presence of
DMAP to obtain oxazolidinone 11, together with the
O-Boc derivative 12. The absolute configuration of
compound 8e was deduced from X-ray analysis8 of
compound 11 (Scheme 5).
Reaction of the organotitanium reagent 7 with oxazo-
lidines 1a , 1c, and 1e (Scheme 3) led to the formation of
the â-amino alcohols 9a , 9c, and 9e, respectively, pos-
sessing an allenylsilane function (Table 3). The absolute
configuration of compound 9a was determined from X-ray
analysis.4
sec-BuLi (5 equiv). e sec-BuLi (5 equiv), PMDTA (1,1,4,7,7-
d
pentamethylenetriamine, 5 equiv). f Diastereoisomeric ratios were
determined by 1H NMR analysis of the crude mixture.
Sch em e 2
The absolute configuration of the â-amino alcohols
having either a vinylsilane function 3 or an alkynylsilane
moiety 5 was determined by a chemical correlation
(Scheme 6) from the known compound 10. Hydrogenation
of compounds 3c and 5c furnished the same product 13;
desilylation followed by hydrogenation of products 8c and
5c gave the same amino alcohol 14, thus disclosing an R
absolute configuration for the stereocenter in 5c. Com-
pound 13, which was obtained from 3c or 5c, also exhibits
an R configuration for the created stereocenter in 3c.
Sch em e 3
respectively, in which two stereogenic centers were
created. The action of triphosgene on compound 8c
afforded oxazolidinone 10 whose absolute configuration
was determined previously by X-ray analysis.4
Discu ssion
The preceding results show that this methodology can
be applied for the synthesis of various amino alcohols
Major isomer 8e was isolated from the mixture of four
isomers obtained in the case of the isopropyl substituent.
The action of triphosgene being unsuccessful, amino
(8) The X-ray analysis was performed by Dr. J .-C. Daran in the
Laboratoire de Chimie de Coordination at Toulouse, France.

1498 J . Org. Chem., Vol. 67, No. 5, 2002
Agami et al.
Sch em e 7
Exp er im en ta l Section
Gen er a l Meth od s. H and 13C NMR spectra (CDCl3 solu-
tion) were recorded on a Bruker ARX 250 spectrometer at 250
and 62.9 MHz, respectively; chemical shifts are reported in
ppm from TMS. Optical rotations were determined with a
Perkin-Elmer 141 instrument. All reactions were carried out
under argon. Column chromatography was performed on silica
gel, 230-400 mesh, by using various mixtures of ethyl acetate
(AcOEt) and petroleum ether (PE). Melting points are uncor-
rected. THF was distilled from sodium/benzophenone ketyl.
THF was degassed for 30 min with argon before use. Composi-
tions of stereoisomeric mixtures were determined by NMR
analysis on crude products before any purification.
1
Sch em e 8
Gen er a l P r oced u r e for th e P r ep a r a tion of Oxa zo-
lid in es. The required aldehyde (5.85 mmol) was added drop-
wise to a solution of (2S)-phenylglycinol (800 mg, 5.85 mmol)
in THF (12 mL) in the presence of MgSO4. The mixture was
stirred at room temperature for 1 h (for 1e) or 2 h (for 1f) and
filtered over Celite 545. The solution was concentrated under
reduced pressure to afford a mixture of cis and trans oxazo-
lidines in a quantitative yield. This mixture was engaged in
the next step without further purification.
possessing an unsaturated silane moiety. However, a
limitation was found when a 2-methyl-substituted ox-
azolidine was used as a substrate (see entries 2 and 8 in
Table 1). This unsatisfactory result can be ascribed to
the instability of such oxazolidine2b whose methyl moiety
is very sensitive to a base-mediated deprotonation.
(4S)-2-Isop r op yl-4-p h en yloxa zolid in e (1e). Oil. 1H NMR:
7.23-7.11 (m, 5H), 4.33 (t, J ) 7.0 Hz, 0.35H), 4.26-4.19 (m,
1.65H), 4.12 (dd, J ) 7.2 and 8.0 Hz, 0.35H), 3.99 (t, J ) 7.5
Hz, 0.65H), 3.54-3.46 (m, 1H), 2.03 (m, 1H), 1.83-1.66 (m,
1H), 1.00-0.83 (m, 6H).13C NMR: 142.4, 140.4, 128.9, 128.7,
127.9, 127.2, 126.9, 126.5, 97.7, 97.3, 72.7, 71.8, 62.5, 60.8, 32.7,
32.3, 18.5, 18.3, 18.2.
Rationalization of the results (cf Scheme 1) obtained
with the organolithium derivatives 2 or 4 can be made
on the basis of the model described by Block.1a A first
equivalent of organolithium compound reacts with the
oxazolidine to give an imine with an E-geometry, and a
second equivalent attacks this intermediate in an anti
position relative to the phenyl group, as depicted in
Scheme 7.
(4S)-2-ter t-Bu tyl-4-p h en yloxa zolid in e (1f). Oil. 1H NMR:
7.28-7.16 (m, 5H), 4.38 (t, J ) 6.6 Hz, 0.4H), 4.29 (t, J ) 7.7
Hz, 0.6H), 4.27 (s, 0.4H), 4.26 (s, 0.6H), 4.19-4.13 (m, 0.4H),
4.07 (t, J ) 7.5 Hz, 0.6H), 3.60 (dd, J ) 6.5 and 8.1 Hz, 0.4H),
3.52 (t, J ) 7.7 Hz, 0.6H), 1.94 (s, 1H), 0.95-0.92 (m, 9H). 13
C
NMR: 142.3, 140.2, 128.9, 128.7, 128.5, 127.9, 127.3, 127.0,
126.6, 99.7, 99.3, 73.1, 72.2, 62.4, 61.0, 34.4, 33.8, 25.4, 25.3.
Gen er a l P r oced u r e for th e Syn th eses of â-Am in o
Alcoh ols 3a -f a n d 5a -e. sec-Butyllithium (1.3 M in cyclo-
hexane, 3.4 mL, 4.40 mmol) was added at -78 °C to a solution
of allyltrimethylsilane (0.70 mL, 4.40 mmol) (for 3) or pro-
pyntrimethylsilane (0.65 mL, 4.40 mmol) (for 5) and tetra-
methylethylenediamine (0.65 mL, 4.40 mmol) in THF (8 mL).
After stirring for 15 min at -78 °C and 15 min at room
temperature, the mixture was cooled at -78 °C and a solution
of oxazolidine (0.88 mmol) in THF (4 mL) was added dropwise.
After an additional stirring of 20 min at this temperature, the
mixture was allowed to reach 0 °C in 1 h, and the reaction
was then quenched by addition of an aqueous solution satu-
rated with NH4Cl (15 mL). The aqueous layer was extracted
with Et2O (3 × 15 mL), and the organic layers were combined,
dried over K2CO3, and evaporated. The residue was then
chromatographed on silica gel.
The change of regioselectivity observed with titanium
isopropoxide can be ascribed to the nature of the orga-
nometallic species. As described above, the titanium
species 6 afforded amino alcohols 8c and 8e from oxazo-
lidines 1c and 1e (Schemes 4 and 5). The complete
stereoselectivity observed during the formation of com-
pound 8c can be rationalized by a chair cyclic transition
state, analogous to the transition state involved in the
case of addition of allyltitanium derivatives onto imines9
(Scheme 8). In such a fixed conformation, the pseudoaxial
geometry of the ethyl group of the imine and the chelation
between titanium, nitrogen, and oxygen atoms explain
the favored attack on the Si face of the imine. In this
transition state, the bulky phenyl group occupies a
pseudoequatorial position.
[2S,2(1S)]-2-P h en yl-2-(1-p h en yl-4-tr im eth ylsila n ylbu t-
3-en yla m in o)eth a n ol (3a ). Oil (AcOEt/PE, 10:90). Yield:
81%. 1H NMR: 7.27-7.16 (m, 10H), 5.86 (dt, J ) 6.5 and 18.5
Hz, 1H), 5.65 (d, J ) 18.5 Hz, 1H), 3.84 (dd, J ) 4.5 and 7.0
Hz, 1H), 3.76-3.69 (m, 2H), 3.50 (dd, J ) 7.0 and 10.5 Hz,
1H), 2.59-2.41 (m, 4H), 0.00 (s, 9H). 13C NMR: 143.8, 143.1,
141.3, 133.8, 128.6, 128.3, 127.4, 126.2, 126.1, 65.6, 61.4, 59.8,
44.5, -1.2.
The selectivity observed during the reaction with the
titanium derivative 7 could hardly be explained by a
chairlike transition state, which is incompatible with the
geometry of the triple bond. An open transition state
analogous to those involved in the attack of organo-
lithium derivative (Scheme 7) can be also operative
during the formation of â-amino alcohols 9. The excellent
stereoselectivity that results from such open transition
states was already pointed out.1a
[2(1R),2S]-2-(1-Meth yl-4-tr im eth ylsilan ylbu t-3-en ylam i-
n o)-2-p h en yleth a n ol (3b). Oil (AcOEt/PE, 15:85). Yield:
1
26%. H NMR: 7.30-7.21 (m, 5H), 5.93 (dt, J ) 6.6 and 18.5
Hz, 1H), 5.65 (d, J ) 18 Hz, 1H), 3.83 (dd, J ) 4.4 and 8.6 Hz,
1H), 3.61 (dd, J ) 4.4 and 10.6 Hz, 1H), 3.40 (dd, J ) 8.6 and
10.6 Hz, 1H), 2.70-2.63 (m, 1H), 2.50-2.20 (m, 2H), 2.31-
2.22 (m, 1H), 2.14-2.03 (m, 1H), 0.93 (d, J ) 7. 5 Hz, 3H),
0.01-0.04 (m, 9H). 13C NMR: 143.6, 141.6, 133.5, 128.7, 127.6,
127.2, 66.8, 61.9, 50.1, 43.7, 21.7, -1.1.
In conclusion, we have synthesized a large range of
â-amino alcohols variously functionalized. These com-
pounds present considerable interest as starting materi-
als in asymmetric syntheses. Further studies on the
synthetic applications of these compounds are actively
underway.
[2(1R),2S]-2-(1-Eth yl-4-tr im eth ylsila n ylbu t-3-en yla m i-
n o)-2-p h en yleth a n ol (3c). Oil (AcOEt/PE, 15:85). Yield:
45%. [R]20D: +87 (c 0.9, CHCl3). 1H NMR: 7.31-7.17 (m, 5H),
5.94 (dt, J ) 6.5 and 18.5 Hz, 1H), 5.67 (dd, J ) 0.9 and 18.5
Hz, 1H), 3.85 (dd, J ) 4.6 and 8.6 Hz, 1H), 3.60 (dd, J ) 4.6
(9) (a) Yamamoto, Y.; Asao, N. Chem. Rev. 1993, 93, 2207. (b)
Okamoto, S.; Fukuhara, K.; Sato, F. Tetrahedron Lett. 2000, 41, 5561.

New Functionalized â-Amino Alcohols
J . Org. Chem., Vol. 67, No. 5, 2002 1499
and 10.5 Hz, 1H), 3.43 (dd, J ) 8.6 and 10.5 Hz, 1H), 2.75 (bs,
2H), 2.48-2.39 (m, 1H), 2.25-2.18 (m, 2H), 1.40-1.20 (m, 2H),
0.76 (t, J ) 7.4 Hz, 3H), 0.00 (s, 9H).13C NMR: 143.4, 141.2,
133.5, 128.6, 127.6, 127.3, 66.8, 61.8, 55.5, 40.5, 27.6, 10.4,
-1.1. Anal. Calcd for C17H29NOSi: C, 70.04; H, 10.33; N, 4.80.
Found: C, 69.92; H, 10.15; N, 4.61.
13C NMR: 141.1, 128.6, 127.6, 127.3, 104.4, 87.0, 67.3, 61.6,
52.6, 37.3, 24.8, 19.2, 14.1, 0.2. Anal. Calcd for C18H29NOSi:
C, 71.23; H, 9.63, N, 4.61. Found: C, 71.24; H, 9.54; N, 4.68.
[2S,2(1S)]-2-P h en yl-2-(1-isop r op yl-4-tr im eth ylsila n yl-
bu t-3-yn yla m in o)eth a n ol (5e). Solid (AcOEt/PE, 10:90).
Yield: 68%. Mp: 43 °C. [R]20D: +114 (c 1.0, CHCl3). 1H NMR:
7.20-7.06 (m, 5H), 3.75 (dd, J ) 4.5 and 8.5 Hz, 1H), 3.53
(dd, J ) 4.5 and 10.5 Hz, 1H), 3.34 (dd, J ) 8.5 and 10.5 Hz,
1H), 2.38-2.11 (m, 3H), 2.15-1.85 (m, 2H), 1.70-1.55 (m, 1H),
0.75 (d, J ) 7.5 Hz, 3H), 0.68 (d, J ) 7.5 Hz, 3H), 0.0 (s, 9H).13C
NMR: 141.2, 128.6, 127.6, 127.5, 105.1, 86.8, 67.5, 62.1, 58.6,
31.6, 22.2, 19.1, 18.8, 0.2. Anal. Calcd for C18H29NOSi: C,
71.23; H, 9.63; N, 4.61. Found: C, 71.01, H, 9.72; N, 4.68.
[2S,2(1R)]-2-P h en yl-2-(1-p r op yl-4-tr im eth ylsila n ylbu t-
3-en yla m in o)eth a n ol (3d ). Oil (AcOEt/PE, 20:80). Yield:
46%. [R]20D: +84 (c 1.4, CHCl3). 1H NMR: 7.32-7.18 (m, 5H),
5.94 (dt, J ) 6.6 and 18.5 Hz, 1H), 5.67 (dt, J ) 1.0 and 18.5
Hz, 1H), 3.83 (dd, J ) 4.5 and 8.6 Hz, 1H), 3.60 (dd, J ) 4.5
and 10.6 Hz, 1H), 3.42 (dd, J ) 8.6 and 10.6 Hz, 1H), 2.52-
2.48 (m, 1H), 2.35 (bs, 2H), 2.22-2.17 (m, 2H), 1.30-1.11 (m,
4H), 0.73 (t, J ) 7.0 Hz, 3H), 0.00 (s, 9H).13C NMR: 143.6,
141.4, 133.5, 128.6, 127.6, 127.3, 66.9, 61.7, 53.7, 41.1, 37.3,
Gen er a l P r oced u r e for th e Syn th eses of â-Am in o
Alcoh ols 8c, 8e, a n d 9. sec-Butyllithium (1.3 M in cyclohex-
ane, 3.4 mL, 4.40 mmol) was added at -78 °C to a solution of
allyltrimethylsilane (for 8c and 8e) or propyntrimethylsilane
(for 9) (4.40 mmol) and tetramethylethylenediamine (0.65 mL,
4.40 mmol) in THF (8 mL). After stirring for 15 min at -78
°C and 15 min at room temperature, the mixture was cooled
at -78 °C and titanium isopropoxide (1.35 mL, 4.40 mmol)
was added slowly. The mixture was stirred at -78 °C for 1 h,
and a solution of oxazolidine (0.88 mmol) in THF (4 mL) was
added dropwise. After an additionnal stirring of 20 min at this
temperature, the mixture was allowed to reach 0 °C in 1 h,
and the reaction was then quenched by addition of an aqueous
solution saturated with NH4Cl (15 mL) and water (15 mL).
The aqueous layer was extracted with Et2O (3 × 15 mL), and
the organic layers were combined, dried over K2CO3, and
evaporated. The residue was then chromatographed on silica
gel.
19.1, 14.2, -1.1. IR: 3326, 2956, 1615, 1454 cm-1
.
[2S,2(1R)]-2-P h en yl-2-(1-isop r op yl-4-tr im eth ylsila n yl-
b u t -3-en yla m in o)et h a n ol (3e). Oil (AcOEt/PE, 15:85).
1
Yield: 75%. [R]20D: +96 (c 1.5, CHCl3). H NMR: 7.30-7.17
(m, 5H), 5.96 (dt, J ) 6.5 and 18.5 Hz, 1H), 5.67 (dt, J ) 1.2
and 18.5 Hz, 1H), 3.80 (dd, J ) 4.5 and 8.5 Hz, 1H), 3.59 (dd,
J ) 4.5 and 10.5 Hz, 1H), 3.40 (dd, J ) 8.5 and 10.5 Hz, 1H),
2.70 (bs, 1H), 2.32-2.28 (m, 1H), 2.22-2.17 (m, 2H), 1.65-
1.52 (m, 2H), 0.79 (d, J ) 6.7 Hz, 3H), 0.73 (d, J ) 6.7 Hz,
3H), 0.00 (m, 9H). 13C NMR: 144.7, 141.7, 133.0, 128.7, 127.6,
127.5, 67.1, 62.1, 59.7, 38.5, 31.0, 18.8, 18.5, -1.0. Anal. Calcd
for C18H31NOSi: C, 70.76; H, 10.23; N, 4.58. Found: C, 70.61;
H, 10.23; N, 4.41.
[2(1R),2S]-2-(1-ter t-Bu tyl-4-tr im eth ylsila n ylbu t-3-en yl-
a m in o)-2-p h en yleth a n ol (3f). Oil (AcOEt/PE, 15:85). Yield:
80%. [R]20D: +119 (c 0.9, CHCl3). 1H NMR: 7.29-7.16 (m, 5H),
6.09-5.97 (m, 1H), 5.68-5.60 (m, 1H), 3.88 (dd, J ) 4.6 and
8.5 Hz, 1H), 3.58 (dd, J ) 4.6 and 10.6 Hz, 1H), 3.44 (dd, J )
8.5 and 10.6 Hz, 1H), 2.80-2.30 (m, 2H), 2.49-2.40 (m, 1H),
2.19-2.07 (m, 2H), 0.79 (s, 9H), 0.02-0.00 (m, 9H). 13C NMR:
147.0, 141.3, 131.4, 128.5, 127.9, 127.5, 67.2, 62.7, 62.4, 39.3,
35.2, 27.2, -1.5.
[2(1R,2S),2S]-2-(1-Eth yl-2-tr im eth ylsila n ylbu t-3-en yl-
a m in o)-2-p h en ylet h a n ol (8c). Solid (AcOEt/PE, 10:90).
Yield: 50%. Mp: 43 °C. [R]20D: +154 (c 1.2, CHCl3). 1H NMR:
7.39-7.29 (m, 5H), 5.81 (dt, J ) 17.0 and 10.5 Hz, 1H), 5.11
(dd, J ) 10.0 and 2.0 Hz, 1H), 5.04 (dd, J ) 17.0 and 2.2 Hz,
1H), 3.89 (dd, J ) 8.5 and 4.5 Hz, 1H), 3.72 (dd, J ) 10.5 and
4.5 Hz, 1H), 3.60 (dd, J ) 10.5 and 8.5 Hz, 1H), 2.54-2.50 (m,
1H), 2.39 (bs, 2H), 2.10 (dd, J ) 11.0 and 3.7 Hz, 1H), 1.52-
1.33 (m, 2H), 0.90 (t, J ) 7.2 Hz, 3H), 0.00 (s, 9H).13C NMR:
141.1, 135.9, 128.5, 127.6, 127.5, 115.7, 67.2, 61.0, 55.9, 38.8,
25.9, 11.4, -2.0. Anal. Calcd for C17H29NOSi: C, 70.04; H,
10.03; N, 4.80. Found: C, 70.02; H, 10.02; N, 4.76.
[2S,2(1S)]-2-P h en yl-2-(1-p h en yl-4-tr im eth ylsila n ylbu t-
3-yn yla m in o)eth a n ol (5a ). Oil (AcOEt/PE, 20:80). Yield:
1
70%. H NMR: 7.23-7.05 (m, 10H), 3.79-3.71 (m, 2H), 3.63
(dd, J ) 4.5 and 10.7 Hz, 1H), 3.42 (dd, J ) 7.2 and 10.7 Hz,
1H), 2.70-2.55 (m, 2H), 2.50 (t, J ) 6.1 Hz, 2H), 0.0 (s, 9H).
13C NMR: 142.9, 140.9, 128.6, 128.3, 127.5, 127.2, 127.0, 104.1,
87.6, 66.0, 61.6, 58.4, 28.3, 0.0. Anal. Calcd for C21H27NOSi:
C, 74.73; H, 8.06; N, 4.15. Found: C, 74.30; H, 8.25; N, 3.98.
[2(1R),2S]-2-(1-Meth yl-4-tr im eth ylsilan ylbu t-3-yn ylam i-
n o)-2-p h en yleth a n ol (5b). Solid (AcOEt/PE, 40:60). Yield:
[2(1R,2S),2S]-2-(1-Isop r op yl-2-t r im et h ylsila n ylb u t -3-
en yla m in o)-2-p h en yleth a n ol (8e). Oil (AcOEt/PE, 7:93).
1
Yield: 48%. Mp: 64 °C. [R]20D: +37 (c 0.6, CHCl3). H NMR:
1
17%. Mp: 94 °C. [R]20D: +94 (c 0.6, CHCl3). H NMR: 7.31-
7.25-7.14 (m, 5H), 5.85 (dt, J ) 16.7 and 10.5 Hz, 1H), 4.86
(dd, J ) 10.0 and 2.0 Hz, 1H), 4.81 (dd, J ) 16.7 and 2.2 Hz,
1H), 3.72 (dd, J ) 7.2 and 5.2 Hz, 1H), 3.58 (dd, J ) 10.7 and
7.2 Hz, 1H), 3.56 (dd, J ) 10.7 and 5.2 Hz, 1H), 2.62 (t, J )
4.0 Hz, 1H), 2.30-1.50 (m, 2H), 1.81 (dd, J ) 11.0 and 4.5 Hz,
1H), 1.72-1.60 (m, 1H), 0.71 (d, J ) 5.0 Hz, 3H), 0.57 (d, J )
7.5 Hz, 3H), 0.00 (s, 9H).13C NMR: 142.4, 138.1, 128.3, 127.4,
127.3, 113.7, 66.4, 63.2, 60.3, 38.6, 32.6, 18.4, 18.3, 0.0. Anal.
Calcd for C18H31NOSi: C, 70.76; H, 10.23; N, 4.58. Found: C,
70.64; H, 10.28; N, 4.42.
7.16 (m, 5H), 3.80 (dd, J ) 4.5 and 8.7 Hz, 1H), 3.60 (dd, J )
4.5 and 10.5 Hz, 1H), 3.40 (dd, J ) 8.7 and 10.5 Hz, 1H), 2.80-
2.68 (m, 1H), 2.37-2.17 (ABX system, J AB ) 17 Hz, J AX ) 4.7
Hz, J BX ) 5.8 Hz, 2H), 2.40-1.90 (m, 2H), 1.02 (d, J ) 7.5 Hz,
3H), 0.04 (s, 9H). 13C NMR: 141.3, 128.7, 127.7, 127.2, 104.3,
87.0, 67.1, 61.9, 49.2, 27.0, 21.6, 0.2. Anal. Calcd for C16H25
-
NOSi: C, 69.76; H, 9.15; N, 5.08. Found: C, 69.92; H, 9.11;
N, 4.86.
[2(1R),2S]-2-(1-Eth yl-4-tr im eth ylsila n ylbu t-3-yn yla m i-
n o)-2-p h en yleth a n ol (5c). Solid (AcOEt/PE, 20:80). Yield:
55%. Mp: 78 °C. [R]20D: +108 (c 1.1, CHCl3). 1H NMR: 7.22-
7.08 (m, 5H), 3.74 (dd, J ) 4.4 and 8.6 Hz, 1H), 3.52 (dd, J )
4.4 and 10.6 Hz, 1H), 3.32 (dd, J ) 8.6 and 10.6 Hz, 1H), 2.40-
[2S,2(1R)]-2-P h en yl-2-(1-ph en yl-4-tr im eth ylsilan ylbu ta-
2,3-d ien yla m in o)eth a n ol (9a ). Solid (AcOEt/PE, 12:88).
1
Yield: 78%. Mp: 49 °C. [R]20D: -97 (c 0.9, CHCl3). H NMR:
7.47-7.31 (m, 5H), 4.87 (dd, J ) 2.5 and 11.0 Hz, 1H), 4.81
(dd, J ) 2.5 and 11 Hz, 1H), 4.21 (t, J ) 2.5 Hz, 1H), 4.08 (dd,
J ) 4.5 and 8.5 Hz, 1H), 3.82 (dd, J ) 4.5 and 10.5 Hz, 1H),
3.65 (dd, J ) 8.5 and 10.5 Hz, 1H), 2.49 (bs, 2H), 0.0 (t, J )
2.5 Hz, 9H). 13C NMR: 208.7, 143.4, 140.9, 128.7, 128.4, 127.9,
127.7, 127.4, 98.6, 72.2, 67.1, 62.4, 58.8, -1.3. Anal. Calcd for
2.32 (m, 1H), 2.36-2.07 (ABX system, J AB ) 16.6 Hz, J AX
)
4.2 Hz, J BX ) 5.5 Hz, 2H), 1.99 (bs, 2H), 1.38-1.26 (m, 2H),
0.69 (t, J ) 7.5 Hz, 3H), 0.0 (s, 9H). 13C NMR: 141.1, 128.5,
127.5, 127.2, 104.2, 88.0, 67.2, 61.6, 54.4, 27.7, 24.3, 10.5, 0.3.
Anal. Calcd for C17H27NOSi: C, 70.53; H, 9.40; N, 4.83.
Found: C, 70.44; H, 9.57; N, 4.82.
C
21H27NOSi: C, 74.73; H, 8.06; N, 4.15. Found: C, 74.71; H,
[2S,2(1R)]-2-P h en yl-2-(1-p r op yl-4-tr im eth ylsila n ylbu t-
3-yn yla m in o)eth a n ol (5d ). Solid (AcOEt/PE, 20:80). Yield:
8.09; N, 3.99.
1
55%. Mp: 66 °C. [R]20D: +99 (c 1.1, CHCl3). H NMR: 7.20-
[2(1R),2S]-2-(1-Eth yl-2-tr im eth ylsilan ylbu ta-2,3-dien yl-
a m in o)-2-p h en yleth a n ol (9c). Oil (AcOEt/PE, 8:92). Yield:
7.06 (m, 5H), 3.94 (dd, J ) 4.5 and 8.6 Hz, 1H), 3.73 (dd, J )
4.5 and 10.5 Hz, 1H), 3.32 (dd, J ) 10.5 and 8.5 Hz, 1H), 2.49-
2.40 (m, 1H), 2.30 (ABX, J AB ) 16.8 Hz, and J AX ) 5.6 Hz,
1H), 2.20 (bs, 2H), 2.10 (ABX, J AB ) 16.8 and J BX ) 4.2 Hz,
1H), 1.33-1.04 (m, 4H), 0.66 (t, J ) 7.4 Hz, 3H), 0.00 (s, 9H).
1
70%. H NMR: 7.31-7.18 (m, 5H), 4.49 (dd, J ) 1.5 and 10.8
Hz, 1H), 4.41 (dd, J ) 1.3 and 10.8 Hz, 1H), 3.82 (dd, J ) 4.8
and 8.8 Hz, 1H), 3.60 (dd, J ) 4.8 and 10.8 Hz, 1H), 3.47 (dd,
J ) 8.8 and 10.8 Hz, 1H), 2.84-2.78 (m, 1H), 2.39 (bs, 2H),

1500 J . Org. Chem., Vol. 67, No. 5, 2002
Agami et al.
1.51-1.34 (m, 2H), 0.91-0.88 (t, J ) 7.5 Hz, 3H), 0.0 (s, 9H).
13C NMR: 208.3, 140.9, 128.5, 128.4, 127.4, 98.4, 71.0, 67.6,
61.8, 56.3, 30.3, 10.6, -1.0.
might be related to a mix up of solvent molecules (hexane,
pentane, Et2O, etc.), but no correct models could be defined.
Least-squares refinements were carried out by minimizing the
function Σw(Fo - Fc2)2, where Fo and Fc are the observed and
2
[2(1R),2S]-2-(1-Isop r op yl-2-t r im et h ylsila n ylb u t a -2,3-
d ien yla m in o)-2-p h en yleth a n ol (9e). Oil (AcOEt/PE, 10:90).
calculated structure factors. The weighting scheme used in the
last refinement cycles was w ) 1/[σ2(Fo2) + (aP)2 + bP], where
1
Yield: 55%. [R]20D: +159 (c 1.0, CHCl3). H NMR: 7.35-7.20
2
P ) (Fo + 2Fc2)/3. Models reached convergence with R ) Σ-
(m, 5H), 4.56 (dd, J ) 1.5 and 10.8 Hz, 1H), 4.45 (dd, J ) 1.3
and 10.8 Hz, 1H), 3.82 (dd, J ) 4.5 and 8.8 Hz, 1H), 3.64 (dd,
J ) 4.5 and 10.8 Hz, 1H), 3.53 (dd, J ) 8.8 and 10.8 Hz, 1H),
2.73-2.70 (m, 1H), 2.53 (bs, 2H), 1.70-1.62 (m, 1H), 0.91-
0.88 (m, 6H), 0.0 (t, J ) 2.5 Hz, 9H). 13C NMR: 208.5, 140.7,
128.3, 127.8, 127.4, 97.6, 70.9, 67.7, 62.0, 59.7, 33.4, 20.5, 16.7,
-1.0.
2
(||Fo| - |Fc||)/Σ(|Fo|) and wR2 ) {Σw(Fo - Fc2)2/Σw(Fo2)2}1/2
,
having values listed in Table 1. The calculations were carried
out with the SHELXL-97 program11 using the integrated
system WINGX(1.63).12 A molecular view was realized with
the help of ORTEP.13 Crystallographic data (excluding struc-
ture factors) for the structure reported in this paper have been
deposited with the Cambridge Crystallographic Data Centre
as supplementary publication no. CCDC-178136. Copies of the
data can be obtained free of charge upon application to CCDC,
12 Union Road, Cambridge CB2 IEZ, U.K. [Fax: int. code +44-
(1223)336-033; E-mail: deposit@ccdc.cam.ac.uk].
[3(1R,2S),4S]-3-(1-Eth yl-2-tr im eth ylsila n ylbu t-3-en yl)-
4-p h en yloxa zolid in -2-on e (10). An aqueous solution of 6 N
NaOH (1.6 mL) was added to a vigorously stirred solution of
amino alcohol 8c (2.0 mmol) in CH2Cl2 (4.5 mL). The mixture
was cooled to -5 °C, and triphosgene (237 mg, 0.8 mmol) in
CH2Cl2 (1.6 mL) was added dropwise over a period of 30 min.
After the mixture was stirred for 4 h at room temperature,
water (15 mL) was added and the resulting mixture was
extracted with CH2Cl2 (3 × 15 mL). After evaporation, the
resulting mixture was chromatographed to give starting
material 8c (yield 29%) and compound 10 as a solid (AcOEt/
PE, 5:95). Yield: 53%. Mp: 141 °C. [R]20D: +104 (c 1.0, CHCl3).
1H NMR: 7.48-7.37 (m, 5H), 5.80 (dt, J ) 10.8 and 16.8 Hz,
1H), 4.89 (dd, J ) 2.0 and 10.0 Hz, 1H), 4.83-4.68 (m, 2H),
4.62 (t, J ) 8.8 Hz, 1H), 4.20 (dd, J ) 7.5 and 8.8 Hz, 1H),
3.23-3.15 (m, 1H), 2.56-2.37 (m, 1H), 2.07 (dd, J ) 5.3 and
10.8 Hz, 1H), 1.53-1.37 (m, 1H), 0.88 (t, J ) 7.5 Hz, 3H), 0.0
(s, 9H). 13C NMR: 158.1, 138.8, 135.3, 129.3, 128.1, 115.0, 69.9,
60.1, 57.3, 39.8, 23.1, 12.1, -2.1. Anal. Calcd for C18H27NO2-
Si: C, 68.09; H, 8.57; N, 4.41. Found: C, 68.03; H, 8.62; N,
4.35.
Com p ou n d (12): Oil. Yield: 46%. 1H NMR: 7.39-7.20 (m,
5H), 5.87 (dt, J ) 10.5 and 16.7 Hz, 1H), 4.93-4.82 (m, 2H),
4.19-4.00 (m, 3H), 2.67 (t, J ) 3.9 Hz, 1H), 1.86 (dd, J ) 4.3
and 11.0 Hz, 1H), 1.78-1.68 (m, 1H), 1.43 (s, 9H), 0.83 (d, J )
6.7 Hz, 3H), 0.69 (d, J ) 7.0 Hz, 3H), 0.02 (s, 9H). 13C NMR:
153.5, 141.6, 137.8, 128.4, 128.0, 127.6, 113.9, 81.8, 71.0, 60.2,
59.7, 39.0, 32.9, 27.8, 18.9, 18.3, -1.9.
[1(1R),2S]-1-(1-Eth yl-4-tr im eth ylsila n ylbu tyla m in o)-2-
p h en yleth a n ol (13). A mixture of amino alcohol 3c or 5c (0.32
mmol) and palladium on carbon (8 mg) in absolute ethanol (5
mL) was hydrogenated under stirring for 2 h. After filtration
over Celite 545 and evaporation, the crude product was
chromatographed to afford compound 13 as an oil. Yield 57%
1
from 3c and 67% from 5c. H NMR: 7.39-7.25 (m, 5H), 3.85
(dd, J ) 4.5 and 8.5 Hz, 1H), 3.69 (dd, J ) 4.5 and 10.5 Hz,
1H), 3.49 (dd, J ) 8.5 and 10.5 Hz, 1H), 2.46-2.35 (m, 1H),
2.40-2.10 (m, 2H), 1.50-1.28 (m, 6H), 0.81 (t, J ) 7.5 Hz, 3H),
0.48 (dd, J ) 7.5 and 8.0 Hz, 2H), 0.00 (s, 9H). 13C NMR: 141.8,
128.6, 127.5, 127.2, 66.7, 61.7, 55.8, 37.5, 27.4, 19.7, 17.1, 10.2,
-1.5.
[3(1R,2R),4S]-3-(1-Isop r op yl-2-t r im et h ylsila n ylb u t -3-
en yl)-4-p h en yloxa zolid in -2-on e (11) a n d [2(1R,2R),2S]-
Ca r bon ic Acid -ter t-bu tylester -2-(1-iso-p r op yl-2-tr im eth -
ylsila n yl bu t-3-en yla m in o)-2-p h en ylester (12). Di-tert-
butyl dicarbonate (200 mg, 0.89 mmol) in AcOEt (10 mL) was
added to a solution of amino alcohol 8e (248 mg, 0.81 mmol)
and DMAP (100 mg, 0.81 mmol) in AcOEt (20 mL). The
mixture was stirred at room temperature for 1 h, evaporated,
and chromatographed to afford compound 12 (152 mg) and
oxazolidinone 11 (109 mg).
[1(1R),2S]-1-(1-Eth ylbu tyla m in o)-2-p h en yleth a n ol (14).
A solution of n-Bu4NF (1 M in THF, 640 µL, 0.64 mmol) was
added to a solution of â-amino alcohol 5c or 8c (0.32 mmol) in
THF (3 mL). The mixture was stirred for 1 h, and water was
added. Extraction with Et2O and evaporation of the organic
layers gave a mixture that was treated with palladium on
carbon (8 mg) in absolute ethanol (5 mL) under an atmosphere
of hydrogen. After stirring for 40 min, filtration over Celite
545, and evaporation, the crude product was chromatographed
to afford amino alcohol 14 as an oil. Yield: 89% (from 5c) and
Com p ou n d (11). Solid. Yield: 42%. Mp: 108 °C. [R]20
:
D
+27 (c 1.0, CHCl3). 1H NMR: 7.39-7.28 (m, 5H), 5.53 (dt, J )
10.4 and 17.0 Hz, 1H), 4.94 (dd, J ) 1.8 and 10.4 Hz, 1H),
4.85 (dd, J ) 1.5 and 17.0 Hz, 1H), 4.66 (dd, J ) 5.7 and 9.0
Hz, 1H), 4.53 (t, J ) 8.7 Hz, 1H), 4.23 (dd, J ) 5.7 and 8.5 Hz,
1H), 3.27-3.21 (m, 1H), 2.42 (t, J ) 10.1 Hz, 1H), 2.05-1.92
(m, 1H), 0.85 (d, J ) 7.0 Hz, 3H), 0.55 (d, J ) 6.7 Hz, 3H),
0.04-0.00 (m, 9H). 13C NMR: 158.7, 149.2, 137.0, 129.1, 128.8,
127.7, 115.6, 69.6, 63.2, 62.4, 37.1, 31.2, 21.6, 19.4, -1.5. Anal.
Calcd for C19H29NO2Si: C, 68.83; H, 8.82; N, 4.22. Found: C,
68.89; H, 9.10; N, 3.84.
56% (from 8c). [R]20D: +105 (c 1.1, CHCl3) (from 5c) and [R]20
:
D
1
+102 (c 1.1, CHCl3) (from 8c). H NMR: 7.29-7.15 (m, 5H),
3.76 (dd, J ) 4.5 and 8.5 Hz, 1H), 3.59 (dd, J ) 4.5 and 10.5
Hz, 1H), 3.40 (dd, J ) 8.5 and 10.5 Hz, 1H), 2.40-2.27 (m,
3H), 1.38-1.14 (m, 6H), 0.82 (t, J ) 7.0 Hz, 3H), 0.72 (t, J )
7.5 Hz, 3H). 13C NMR: 141.7, 128.6, 127.5, 127.3, 66.7, 61.7,
55.6, 35.6, 27.4, 18.4, 14.6, 10.2. IR: 3391, 2957, 1493, 1455
X-r a y Cr ysta llogr a p h ic Stu d y. Data were collected on a
Brucker Smart 1000 diffractometer. The final unit cell pa-
rameters were obtained by the least-squares refinement of
10 000 reflections. Only statistical fluctuations were observed
in the intensity monitors over the course of the data collections.
The structure was solved by direct methods (SIR9710) and
refined by least-squares procedures on F2. All H atoms
attached to carbon were introduced in calculation in idealized
positions [d(CH) ) 0.96 Å] and treated as riding models. Due
to the value of the Flack’s parameter of 0.1 and to the standard
uncertainty of 0.2, the absolute configuration could not be
unambiguously determined. However, inverting the configu-
ration led to a Flack’s parameter of 0.9(2), and it may be
assumed that the value of 0.1 is indicative of the true
configuration. There is some residual electron density that
develops around the 2-fold screw axis. This electron density
cm-1
.
Ack n ow led gm en t. The authors gratefully acknowl-
edge Dr. J .-C. Daran for the elucidation of the structure
of compound 11 and Dr. L. Hamon for many interesting
discussions.
Su p p or tin g In for m a tion Ava ila ble: X-ray data. This
material is available free of charge via the Internet at
http://pubs.acs.org.
J O010779A
(11) Sheldrick, G. M. SHELX97, Programs for Crystal Structure
Analysis (Release 97-2); Institu¨t fu¨r Anorganische Chemie der Uni-
versita¨t, Tammanstrasse 4, D-3400 Go¨ttingen, Germany, 1998.
(12) Farrugia, L. J . J . Appl. Crystallogr. 1999, 32, 837.
(13) Burnett, M. N.; J ohnson, C. K. ORTEP-IIIsReport ORNL-6895;
Oak Ridge National Laboratory, Oak Ridge, Tennessee, 1996.
(10) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.;
Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagn,
R. J . Appl. Crystallogr. 1999, 32, 115.