s, SiMe3); δC (100 MHz; CDCl3) 146.6Ϫ (ipso-Ph), 137–125 (m,
crude product which was purified by flash chromatography,
2
Ph2PO and remaining Ph), 107.6Ϫ (d, JPC 4.6, COSi), 84.7ϩ
eluting with 1:1 hexane–EtOAc, to give the silylated hemiacetal
28g (7.4 mg, 16%; >96:4 ratio of diastereomers) as an oil, Rf
0.70 (EtOAc); [α]D20 ϩ19.3 (c 1.08 in CHCl3; 86% ee) (Found:
Mϩ Ϫ Me, 511.1846. C32H35O3PSi requires M Ϫ Me, 511.1859);
1
2
(CHBu), 55.4ϩ (d, JPC 72.1, PCH), 47.0 (d, JPC 8.4, CHMe),
33.1Ϫ, 28.5Ϫ, 23.0Ϫ, 14.1ϩ (d, JPC 6.7, Me), 14.0ϩ (Me), 1.3ϩ
3
(SiMe3); m/z 491.2 (10%, Mϩ Ϫ Me) 359 (100), 201.1 (100,
Ph2PO).
νmax/cmϪ1 (CHCl ) 1422 (P–Ph), 1233 (P᎐O); δ (400 MHz;
᎐
3
H
CDCl3) 7.9–7.0 (20H, m, Ph2PO and Ph), 5.83 (1H, d, J 5.2,
PhCH), 3.07 (1H, dd, J 1.9 and 3.9, PCH), 3.05 (1H, m,
MeCH), 0.63 (3H, d, J 7.2, Me), Ϫ0.09 (9H, s, SiMe3); δC (100
MHz; CDCl3) 146.0Ϫ, 138.3Ϫ (ipso-Ph × 2), 134–125 (m, Ph2PO
and remaining Ph), 107.1Ϫ (COSi), 82.2ϩ (CHPh), 60.9ϩ (d,
(2R,3R,4S,5R)-5-Butyl-3-diphenylphosphinoyl-4-methyl-2-
phenyl-2-trimethylsilyloxytetrahydrofuran 28f
By the same general method, syn-25f (288 mg, 0.66 mmol) gave
a crude product which was purified by flash chromatography,
eluting with 1:1 hexane–EtOAc, to give the silylated hemiacetal
28f (216 mg, 64%; <98:2 ratio of diastereomers) as an oil, Rf
0.72 (EtOAc); [α]D20 ϩ14.2 (c 1.06 in CHCl3; 76% ee) (Found:
Mϩ, 506.2380. C30H40O3PSi requires M, 506.2406); νmax/cmϪ1
3
1JPC 70.8, PCH), 41.1ϩ (CHMe), 17.4ϩ (d, JPC 9.5, Me), 1.2ϩ
(SiMe3); m/z 511.2 (15%, Mϩ Ϫ Me), 201.1 (80, Ph2PO). The
relative stereochemistry was determined by a 500 MHz NOESY
experiment.
Also obtained was the hemiacetal 30g (22 mg, 52%) as an oil
which decomposed on standing to the vinyl phosphine oxide 31g
(Found: Mϩ(vin), 436.1494. C29H25O2P requires M, 436.1493); Rf
0.33 (EtOAc); [α]D20 ϩ16.7 (c 0.46 in CHCl3); νmax/cmϪ1 (CHCl3)
(CHCl ) 1552 (Ph), 1423 (P–Ph), 1225 (P᎐O); δ (400 MHz;
᎐
3
H
CDCl3) 7.8–7.0 (15H, m, Ph2PO and Ph), 4.64 (1H, td, J 4.6
and 9.1, CHBu), 2.92 (1H, dd, J 2.8 and 4.2, PCH), 2.85 (1H,
m, CHMe), 1.8–1.3 (6H, m), 0.92 (3H, d, J 7.0, Me), 0.90 (3H,
t, J 7.2, Me), Ϫ0.12 (9H, s, SiMe3); δC (100 MHz; CDCl3)
146.1Ϫ (ipso-Ph), 137–125 (m, Ph2PO and remaining Ph),
3491 (OH), 1416 (P–Ph), 1198 (P᎐O); δ (400 MHz; CDCl3)
᎐
H
7.8–7.1 (20H, m, Ph2PO and Ph × 2), 6.90 (1H, s, OH), 5.83
3
(1H, d, J 6.3, PhCH), 3.06 (1H, ddqd, J 4.3, 6.3, 7.1 and JPH
2
1
107.1Ϫ (d, JPC 4.6, COSi), 81.2ϩ (CHBu), 61.0ϩ (d, JPC 71.4,
16.4, CHMe), 2.90 (1H, t, J 4.3, PCH), 0.46 (3H, d, J 7.1, Me);
δC (100 MHz; CDCl3) 142.8Ϫ, 138.1Ϫ (ipso-Ph × 2), 132–126 (m,
Ph2PO and remaining Ph), 104.9Ϫ (COH), 80.9ϩ (CHPh), 57.3ϩ
(d, 1JPC 67.6, PCH), 39.5ϩ (CHMe), 18.4ϩ (d, 3JPC 5.5, Me); m/z
436.2 (10%, Mϩ(vin)), 201.1 (90, Ph2PO), 105.0 (100, PhCO), 77
(90, Ph). The relative stereochemistry was determined by a 500
MHz NOESY experiment.
PCH), 39.1ϩ (CHMe), 29.9Ϫ, 28.9Ϫ, 23.0Ϫ, 16.1ϩ (d, JPC 9.3,
3
Me), 14.0ϩ (Me), 1.2ϩ (SiMe3); m/z 506.2 (10%, Mϩ), 201.1
(100, Ph2PO).
TLC analysis showed that another compound appeared on
work-up: also obtained were the hemiacetals 30f (63 mg, 20%,
87:13 ratio of diastereomers) as an oil. On standing, the
hemiacetals decomposed slowly to the vinyl phosphine oxide 31f,
Rf 0.25 (1:1 hexane–EtOAc); δH (400 MHz; CDCl3) 7.8–7.0 (m,
Ph2PO and Ph), 4.63 (1H, dt, J 5.2 and 8.2, BuCHvin), 4.46 (1H,
td, J 5.3 and 7.7, BuCHmajor hemiacetal), 3.63 (1H, td, J 3.4 and 8.9,
Treatment of silylated hemiacetal 29a with dihydroaluminium
chloride
BuCHminor hemiacetal), 2.9–0.8 (m); δC (100 MHz; CDCl3) 166.9Ϫ
Lithium aluminium hydride (9.4 mg, 0.24 mmol) and alu-
minium trichloride (9.4 mg, 70 µmol) were stirred in ether
(2 cm3) at 0 ЊC for 5 min. The reaction mixture was warmed
to room temperature and a solution of the silylated hemiacetal
29a (32 mg, 64 µmol) in ether (2 cm3) was added dropwise. The
reaction was stirred for 2 h, quenched with water (3 cm3),
extracted with dichloromethane (3 × 3 cm3), dried (MgSO4)
and evaporated under reduced pressure to give a crude product.
Flash chromatography, eluting with 2:1 EtOAc-–hexane, gave
the tetrahydrofurans 43 (22 mg, 69%; 58:42 mixture) as an oil,
Rf 0.62 (EtOAc); [α]D20 ϩ10.8 (c 2.10 in CHCl3; 76% ee) (Found:
Mϩ, 404.1915. C26H29O2P requires M, 404.1905); νmax/cmϪ1
2
(d, JPC 18.7, PC᎐Cvin), 143.0Ϫ (ipso-Phhemiacetal), 135–125 (m,
᎐
Ph2PO and remaining Ph), 106.5Ϫ (d, 1JPC 118, PCvin), 104.6Ϫ (d,
2JPC 1.4, COHhemiacetal), 86.4ϩ (d, JPC 9.9, CHBuvin/hemiacetal),
3
79.6ϩ (d, JPC 4.0, CHBuhemiacetal/vin), 57.7ϩ (d, JPC 67.9,
PCHhemiacetal), 44.0ϩ (CHMe), 37.9ϩ (CHMe), 34–22Ϫ (m, CH2),
17–14ϩ (m, Me).
3
1
(2R,3R,4R,5S)-2,5-Diphenyl-3-diphenylphosphinoyl-4-methyl-2-
trimethylsilyloxytetrahydrofuran 27g
By the same general method, anti-25g (36 mg, 79 µmol) gave a
crude product which was purified by flash chromatography,
eluting with 2:1 hexane–EtOAc, to give the silylated hemiacetal
27g (9 mg, 22%; 91:9 ratio of diastereomers) as an oil, Rf 0.63
(2:1 EtOAc–EtOAc); δH (400 MHz; CDCl3) 7.8–7.1 (20H, m,
Ph2PO and 2 × Ph), 5.31 (1H, d, J 10.3, PhCH), 3.53 (1H, dd,
J 3.6 and 9.2, PCH), 2.73 (1H, qddd, J 7.1, 9.2, 9.9 and 24.3,
CHMe), 0.88 (3H, d, J 7.2, Me), Ϫ0.06 (9H, s, SiMe3).
(CHCl ) 1438 (P–Ph), 1177 (P᎐O); δ (400 MHz; CDCl3) 7.8–
᎐
3
H
6.8 (15H, m, Ph2PO and Ph), 5.32 (1H, dd, J 6.8 and 11.9,
PhCHmajor), 5.08 (1H, dd, J 7.7 and 12.7, PhCHminor), 4.61 (1H,
m, BuCHmajor), 4.13 (1H, m, BuCHminor), 3.51 (1H, dq, J 4.0 and
8.1, PCHmajor), 3.02 (1H, tt, J 5.1 and 6.8, PCHminor), 2.70 (1H,
m, major), 2.52 (1H, m, minor), 2.1–1.3 (7H, m), 0.85 (3H, m,
Memajor ϩ minor); δC (100 MHz; CDCl3) 141.3Ϫ (ipso-Phminor),
137.8Ϫ (d, J 4.4, ipso-Phmajor), 135–126 (m, Ph2PO and remain-
ing Ph), 81.8ϩ (PhCHmajor), 80.3ϩ (PhCHminor), 79.9ϩ (d, 3JPC 4.0,
In a separate experiment, the silylated hemiacetal 27g
decomposed on workup: a 32:68 mixture of the silyl ether 27g
and the vinyl phosphine oxide 31g, Rf 0.62 (EtOAc); [α]D20 ϩ25.3
(c 0.60 in CHCl3; 76% ee) (Found: Mϩ, 408.1754. C26H27O2P
requires M, 408.1748); νmax/cmϪ1 (CHCl ) 1617 (C᎐C), 1438
3
1
BuCHminor), 79.3ϩ (d, JPC 7.5, BuCHmajor), 45.1ϩ (d, JPC 72.7,
PCHminor), 43.2ϩ (d, JPC 74.5, PCHmajor), 35.9Ϫ (major), 34.9Ϫ
1
᎐
3
(minor), 34.1Ϫ (minor), 32.6Ϫ (major), 28.2Ϫ (major ϩ minor),
22.8Ϫ (minor), 22.7Ϫ (major), 14.1ϩ (Memajor), 14.0ϩ (Meminor);
m/z 404.2 (2.7%, Mϩ), 201.1 (100, Ph2POH).
(P–Ph), 1169 (P᎐O); δ (400 MHz; CDCl3) 7.7–7.0 (15H, m,
᎐
H
Ph2PO and Ph), 4.73 (quin, J 7.4, BuCH), 2.88 (1H, ddd, J 2.5,
3
2
2JHH 9.9 and JPH 14.7, PCCHAHB), 2.50 (1H, ddd, J 2.3, JHH
9.9 and 3JPH 14.7, PCCHAHB), 1.8–1.1 (6H, m) and 0.90 (3H, t,
Treatment of silylated hemiacetal with methylmagnesium
bromide
2
J 7.0, Me); δC (100 MHz; CDCl3) 166.5Ϫ (d, JPC 18, PC᎐C),
᎐
1
134–127 (m, Ph2PO and Ph), 97.8Ϫ (d, JPC 120, PC), 82.2ϩ (d,
2
Methylmagnesium bromide (0.11 cm3 of a 3.0 mol dmϪ3 solu-
tion, 0.36 mmol) was added dropwise to a stirred solution of
silylated hemiacetal 29a (33 mg, 67 µmol) in dry toluene
(5 cm3). The reaction was heated at 80 ЊC for 2 days, quenched
with water, extracted with dichloromethane (3 × 5 cm3), dried
(MgSO4) and evaporated under reduced pressure to give a
crude product. Flash chromatography, eluting with 2:1 EtOAc–
hexane, gave the tetrahydrofuran 44 (12 mg, 38%, >95:5 ratio
3JPC 10.0, BuCH), 40.3Ϫ (d, JPC 9.2, PCCH2), 35.6Ϫ, 27.7Ϫ,
22.5Ϫ, 14.0ϩ (Me); m/z 408.1 (100%, Mϩ), 345.1 (65, M Ϫ Bu),
201.1 (60, Ph2PO) were isolated.
(2R,3R,4S,5S)-2,5-Diphenyl-3-diphenylphosphinoyl-4-methyl-2-
trimethylsilyloxytetrahydrofuran 28g
By the same general method, syn-25g (42 mg, 93 µmol) gave a
J. Chem. Soc., Perkin Trans. 1, 1999, 3413–3424
3423