Stereoselectivity of model C22-23 aldol coupling for spirangiens A & B

Article abstract of DOI:10.1016/j.tet.2012.10.008

A model system was prepared to investigate the diastereoselectivity of the key C22-23 aldol coupling for the synthesis of spirangiens A & B. The lithium enolate of model ketone 3 was coupled with the differently protected aldehydes 4 (acetonide) and 5 (silyl) giving 3:1 and 3.5:1 dr, respectively, in favour of the unnatural (S) isomer in both cases. The lack of any significant effect on the aldol stereoselectivity induced by the aldehyde protecting groups contrasts with previous literature reports.

Full text of DOI:10.1016/j.tet.2012.10.008

Supplementary Information for “Stereoselectivity of model C22-23 aldol coupling for spirangiens A &
B” by Claire Gregg and Michael V. Perkins
Supplementary Information for “Stereoselectivity of
model C22-23 aldol coupling for spirangiens A & B”
Claire Gregga and Michael V. Perkinsa
aSchool of Chemical and Physical Sciences, Flinders University, GPO Box 2100,
Adelaide, South Australia 5001, Australia
Contents
1. Experimental procedures.
2. Experimental details and data for compounds 38-41, 8, 42-44 and 12
1
3. H NMR spectra for compounds 3-5, 18, 19 and 21-24
4. 13C NMR spectra for compounds 3-5
5. COSY and NOESY spectra for compounds 18, 19, 21-24
1

Supplementary Information for “Stereoselectivity of model C22-23 aldol coupling for spirangiens A &
B” by Claire Gregg and Michael V. Perkins
Experimental Procedures
MeO
O
OPMB
38
(2R)-Methyl-3-(4-methoxybenzyl)oxy-2-methyl-propionate (38).1
To a stirred solution of (R)-3-hydroxy-2-methyl-propionic acid methyl ester [(R)-9]
(0.94 mL; 8.47 mmol) and para-methoxybenzyl imidate (3.59 g; 12.7 mmol) in Et2O
(25 mL) was added triflic acid (6 x 5 µL aliquots over 6 h with monitoring by TLC
(5% Et2O/CH2Cl2)). The reaction was terminated by addition of 10 mL of Et2O and
the organic mixture was washed with sat. aq. NaHCO3 (30 mL), brine (30 mL), dried
(Na2SO4) and concentrated in vacuo to give a white crystalline solid. The solid was
triturated with X4 (3 x 15 mL), filtered, and the filtrate was concentrated in vacuo to
give a yellow oil. Distillation under reduced pressure gave PMB ether 38 (2.02 g;
o
100%) as a colourless oil. bp. 170-172 C at 0.2 mmHg; Rf = 0.50 (5%
Et2O/CH2Cl2); [α]20D = -5.1 (c 1.18, CHCl3); 1H NMR (400 MHz, CDCl3) δ 7.23 (2H,
d, J = 8.8 Hz, ArH), 6.87 (2H, d, J = 8.8 Hz, ArH), 4.45 (2H, ABq, J = 12.4 Hz,
OCH2PMP), 3.80 (3H, s, ArOCH3), 3.68 (3H, s, C(=O)OCH3), 3.63 (1H, dd, J = 9.2,
7.2 Hz, CHAHBOPMB), 3.45 (1H, dd, J = 9.2, 6.0 Hz, CHAHBOPMB), 2.77 (1H, ddq,
J = 7.2, 6.0, 6.0 Hz, CHCH3), 1.17 (3H, d, J = 7.2 Hz, CHCH3); 13C NMR (101 MHz,
CDCl3) δ 175.4, 159.3, 130.4, 129.3, 113.9, 72.9, 71.8, 55.4, 51.8, 40.3, 14.1.
OH OPMB
39
(2S)-3-(4-methoxybenzyl)oxy-2-methyl-propan-1-ol (39).1
A solution of ester 38 (2.04 g; 8.56 mmol) in THF (10 mL) was added via cannula to
o
a stirring solution of LiAlH4 (780 mg; 20.6 mmol) in THF (20 mL) at 0 C. The
resulting mixture was warmed to rt and stirred for 30 min, then recooled to 0 oC. The
reaction was quenched by dropwise addition of H2O (1.1 mL), NaOH (5 M; 1.1 mL)
and H2O (2.2 mL). The mixture was dried (Na2SO4), filtered (Et2O) and concentrated
in vacuo. Purification by column chromatography (30% Et2O/CH2Cl2) gave alcohol
39 (1.76 g; 98%) as a colourless oil. Rf = 0.37 (30% Et2O/CH2Cl2); [α]20 = -16.9 (c
D
2

Supplementary Information for “Stereoselectivity of model C22-23 aldol coupling for spirangiens A &
B” by Claire Gregg and Michael V. Perkins
1.13, CHCl3); 1H NMR (400 MHz, CDCl3) δ 7.24 (2H, d, J = 8.4 Hz, ArH), 6.87 (2H,
d, J = 8.8 Hz, ArH), 4.43 (2H, s, OCH2PMP), 3.79 (3H, s, OCH3), 3.61-3.55 (2H, m,
CH2OH), 3.49 (1H, dd, J = 8.8, 4.4 Hz, CHAHBOPMB), 3.39 (1H, dd, J = 9.2, 7.6 Hz,
CHAHBOPMB), 2.61 (1H, br s, OH), 2.09-2.01 (1H, m, CHCH3), 0.87 (3H, d, J = 6.8
13
Hz, CHCH3); C NMR (101 MHz, CDCl3) δ 159.4, 130.4, 129.4, 114.0, 75.1, 73.2,
67.8, 55.4, 35.8, 13.7.
OTs OPMB
40
(2R)-3-(4-methoxyphenyl)oxy-2-methyl-1-(toluene-4-sulfonyloxy)-propane (40).2
To a mixture of alcohol 39 (1.74 g; 8.28 mmol) in dry pyridine (5.5 mL) at 0 oC was
added tosyl chloride (2.21 g; 11.6 mmol) and the resulting mixture stirred at 0 oC for 9
h. Cold water (50 mL) was added to quench the reaction and after 15 min the mixture
was extracted with Et2O (3 x 15 mL). The combined organic extracts were washed
successively with 1 M HCl (20 mL), sat. aq. NaHCO3 (20 mL) and brine (20 mL),
dried (Na2SO4) and concentrated in vacuo. Purification by column chromatography
(100% CH2Cl2) gave tosylate 40 (2.99 g; 99%) as a colourless oil. Rf = 0.47 (100%
CH2Cl2); [α]20D = -3.1 (c 1.31, CHCl3); 1H NMR (400 MHz, CDCl3) δ 7.77 (2H, d, J
= 8.4 Hz, ArH), 7.32 (2H, d, J = 8.0 Hz, ArH), 7.16 (2H, d, J = 8.8Hz, ArH), 6.86
(2H, d, J = 8.8 Hz, ArH), 4.33 (2H, s, OCH2PMP), 4.03 (1H, dd, J = 9.2, 5.6 Hz,
CHAHBOPMB), 3.97 (1H, dd, J = 9.2, 5.6 Hz, CHAHBOPMB), 3.81 (3H, s, OCH3),
3.32 (1H, dd, J = 9.2, 5.2 Hz, CHAHBOTs), 3.28 (1H, dd, J = 9.2, 5.2 Hz,
CHAHBOTs), 2.43 (3H, s, ArCH3), 2.09 (1H, m, CHCH3), 0.92 (3H, d, J = 7.2 Hz,
13
CHCH3); C NMR (101 MHz, CDCl3) δ 159.3, 144.7, 133.3, 130.5, 129.9, 129.2,
128.0, 113.9, 72.9, 72.4, 71.0, 55.4, 33.8, 21.7, 13.8.
N
OPMB
41
(3S)-4-(4-methoxyphenyl)oxy-3-methyl-butanenitrile (41).2
To a solution of tosylate 40 (8.06 g; 22.1 mmol) in anhydrous DMSO (88 mL) was
added sodium cyanide (2.28 g; 46.4 mmol). The mixture was stirred at 60 oC for 18 h
3

Supplementary Information for “Stereoselectivity of model C22-23 aldol coupling for spirangiens A &
B” by Claire Gregg and Michael V. Perkins
and then allowed to cool to rt, whereupon it was slowly poured into brine (200 mL).
The resulting mixture was extracted with Et2O (3 x 100 mL), the combined organic
extracts dried (Na2SO4) and concentrated in vacuo. Purification by flash
chromatography (100% CH2Cl2) gave nitrile 41 (4.81 g; 99%) as a colourless oil. Rf
= 0.40 (100% CH2Cl2); [α]20D = -15.9 (c 1.45, CHCl3); 1H NMR (400 MHz, CDCl3) δ
7.24 (2H, d, J = 9.2 Hz, ArH), 6.88 (2H, d, J = 8.8 Hz, ArH), 4.44 (2H, s, OCH2PMP),
3.81 (3H, s, OCH3), 3.43 (1H, dd, J = 9.6, 4.8 Hz, CHAHBOPMB), 3.27 (1H, dd, J =
9.2, 7.6 Hz, CHAHBOPMB), 2.49 (1H, dd, J = 16.4, 5.2 Hz, CHAHBCN), 2.37 (1H,
dd, J = 16.8, 7.2 Hz, CHAHBCN), 2.15-2.09 (1H, m, CHCH3), 1.07 (3H, d, J = 6.8 Hz,
13
CHCH3); C NMR (101 MHz, CDCl3) δ 159.5, 130.2, 129.4, 118.8, 114.0, 73.1,
73.0, 55.4, 31.3, 21.6, 16.4.
O
H
OPMB
8
(3R)-4-(4-methoxybenzyl)oxy-3-methyl-propanal (8). 2
o
To a stirred solution of nitrile 41 (1.09 mg; 4.97 mmol) in CH2Cl2 (50 mL) at -78 C
was added diisobutylaluminium hydride (1 M in toluene; 14.9 mL; 14.9 mmol)
dropwise. The reaction mixture was stirred at -78 oC for 2 h, whereupon 1 M HCl (15
mL) was added and the mixture allowed to warm to rt before pouring into 1 M HCl
(50 mL). The mixture was extracted with CH2Cl2 (3 x 50 mL), the combined organic
extracts were washed with brine (100 mL), dried (Na2SO4) and concentrated in vacuo.
Purification by flash chromatography (buffered silica, 5% Et2O/CH2Cl2) gave
aldehyde 8 (980 mg; 89%) as a colourless oil. Rf = 0.35 (5% Et2O/CH2Cl2); [α]20D = -
6.5 (c 1.38, CHCl3); 1H NMR (400 MHz, CDCl3) δ 9.75 (1H, apt t, J = 2.0 Hz, CHO),
7.23 (2H, d, J = 8.8 Hz, ArH), 6.88 (2H, d, J = 8.8 Hz, ArH), 4.41 (2H, s, OCH2PMP),
3.80 (3H, s, OCH3), 3.39 (1H, dd, J = 9.2, 5.2 Hz, CHAHBOPMB), 3.22 (1H, dd, J =
8.8, 7.6 Hz, CHAHBOPMB), 2.53 (1H, ddd, J = 16.0, 6.4, 2.4 Hz, CHAHBCHO), 2.46-
2.35 (1H, m, CHCH3), 2.26 (1H, ddd, J = 16.0, 6.8, 2.0 Hz, CHAHBCHO), 0.97 (3H,
13
d, J = 6.8 Hz, CHCH3); C NMR (100 MHz, CDCl3) δ 202.5, 159.3, 103.5, 129.3,
113.9, 74.8, 72.9, 55.4, 48.7, 29.3, 17.2.
4

Supplementary Information for “Stereoselectivity of model C22-23 aldol coupling for spirangiens A &
B” by Claire Gregg and Michael V. Perkins
Bn
O
N
O
OH
O
42
[[3-(2R,3R)-4R]-3-(3-hydroxy-2,4-dimethyl-1-oxo-pent-4-enyl)-4-
(phenylmethyl)]-2-oxazolidinone (42).
To a stirred solution of oxazolidine (R)-13 (2.05 g; 8.78 mmol) in CH2Cl2 (18 mL) at
0 oC was added Bu2BOTf (10.5 mL; 1M in CH2Cl2; 10.5 mmol) dropwise giving a red
solution. After 30 min Et3N (1.59 mL; 11.4 mmol) was added and the resulting yellow
solution was stirred for a further 30 min before cooling to -78 oC. Methacrolein (1.45
mL; 17.6 mmol) in CH2Cl2 (5 mL) was added dropwise via cannula and the reaction
o
o
mixture stirred at -78 C for 30 min and then at 0 C for 4 h, at which time the
reaction was quenched by addition of pH 7 buffer (8 mL) and MeOH (8 mL). A
solution of 2:1 MeOH/H2O2 (16 mL) was then added and the mixture stirred at room
temperature for 1 h. The volatiles were removed in vacuo and the resulting slurry was
extracted with CH2Cl2 (3 x 20 mL), the combined organic extracts washed with sat.
aq. NaHCO3 (20 mL) and brine (20 mL), dried (Na2SO4) and concentrated in vacuo.
Purification by column chromatography (buffered silica, 5% Et2O/CH2Cl2) gave aldol
adduct 42 (2.61 g; 98%, >98% ds) as a white solid. Rf = 0.31 (5% Et2O/CH2Cl2);
1
[α]20 = -19.6 (c 1.12, CHCl3); H NMR (400 MHz, CDCl3) δ 7.35-7.31 (2H, m,
D
ArH), 7.29-7.25 (1H, m, ArH) 7.22-7.19 (2H, m, ArH), 5.12 (1H, m,
CHAHBC(CH3)CHOH), 4.97 (1H, m, CHAHBC(CH3)CHOH), 4.71 (1H, m, CHCH2O),
4.42 (1H, s, CHOH), 4.23 (1H, dd, J = 9.6, 9.2 Hz, CHCHAHBO), 4.19 (1H, dd, J =
8.8, 3.2 Hz, CHCHAHBO), 3.98 (1H, dq, J = 7.2, 3.2 Hz, CH(OH)CH(CH3)C=O),
3.27 (1H, dd, J = 13.6, 3.6 Hz, CHAHBPh), 2.94 (1H, br s, OH), 2.80 (1H, dd, J =
13.2, 9.2 Hz, CHAHBPh), 1.74 (3H, s, CH2C(CH3)CHOH), 1.19 (3H, d, J = 7.2 Hz,
13
CH(OH)CH(CH3)C=O); C NMR (100 MHz, CDCl3) δ 177.2, 153.1, 143.9, 135.2,
129.6, 129.1, 127.6, 111.9, 74.1, 66.4, 55.4, 40.3, 37.9, 19.5, 10.2.
5

Supplementary Information for “Stereoselectivity of model C22-23 aldol coupling for spirangiens A &
B” by Claire Gregg and Michael V. Perkins
Bn
O
N
O
O
O
TBS
43
[[3-(2R,3R)-4R]-3-(3-(tert-butyldimethylsilyloxy)-2,4-dimethyl-1-oxo-pent-4-
enyl)-4-(phenylmethyl)]-2-oxazolidinone (43).
The previous procedure used for the preparation of TBS ether 11 was followed with
alcohol 42 (2.67 g; 8.79 mmol), 2,6-lutidine (2.05 mL; 17.6 mmol), TBSOTf (3.03
mL; 13.2 mmol) and CH2Cl2 (88 mL). Purification by column chromatography
(buffered silica, 20% X4/CH2Cl2) gave TBS ether 43 (3.66 g; 100%) as a while solid.
1
Rf = 0.55 20% X4/CH2Cl2); [α]20 = -48.1 (c 1.85, CHCl3); H NMR (400 MHz,
D
CDCl3) δ 7.33-7.29 (2H, m, ArH), 7.26-7.22 (1H, m, ArH) 7.21-7.18 (2H, m, ArH),
4.94 (1H, m, CHAHBC(CH3)CHOH), 4.83 (1H, m, CHAHBC(CH3)CHOH), 4.56 (1H,
m, CHCH2O), 4.36 (1H, d, J = 6.4 Hz, CHOTBS), 4.15-4.08 (2H, m, J = 9.6, 9.2 Hz,
CHCH2O), 4.03 (1H, dq, J = 6.8, 6.8 Hz, CH(OTBS)CH(CH3)C=O), 3.25 (1H, dd, J =
13.6, 3.2 Hz, CHAHBPh), 2.76 (1H, dd, J = 13.6, 9.6 Hz, CHAHBPh), 1.72 (3H, s,
CH2C(CH3)CHOTBS), 1.21 (3H, d, J = 6.8 Hz, CH(OH)CH(CH3)C=O), 0.91 (9H, s,
13
OSiC(CH3)3), 0.02 (3H, s, OSi(CH3)CH3), -0.01 (3H, s, OSi(CH3)CH3); C NMR
(100 MHz, CDCl3) δ 174.9, 153.2, 145.8, 135.5, 129.6, 129.0, 127.5, 112.7, 77.1,
66.1, 55.8, 42.6, 37.8, 25.9, 18.3, 17.9, 12.5, -4.6, -5.2.
O
OH
TBS
44
(2S,3R)-3-(tert-butyldimethylsilyloxy)-2,4-dimethyl-pent-4-en-1-ol (44).
To a stirred solution of oxazolidinone 43 (2.71 g; 6.48 mmol) in Et2O (80 mL) at -10
oC was added EtOH (911 µL; 15.6 mmol) and LiBH4 (15.6 mL; 1 M in THF; 15.6
o
mmol) and the resulting mixture was stirred at -10 C for 4 h. The reaction mixture
o
was warmed to 0 C and quenched by addition of 1 M NaOH (50 mL). The mixture
was poured into brine (50 mL) and extracted with Et2O (4 x 50 mL). The combined
organic extracts were dried (Na2SO4) and concentrated in vacuo. Purification by
column chromatography (buffered silica, 5% Et2O/CH2Cl2) gave alcohol 44 (1.24 g;
6

Supplementary Information for “Stereoselectivity of model C22-23 aldol coupling for spirangiens A &
B” by Claire Gregg and Michael V. Perkins
78%) as a colourless oil. Rf = 0.47 (5% Et2O/CH2Cl2); [α]20 = +17.9 (c 1.45,
D
1
CHCl3); H NMR (400 MHz, CDCl3) δ 4.93 (1H, m, CHAHBC(CH3)CHOH), 4.87
(1H, m, CHAHBC(CH3)CHOH), 4.05 (1H, d, J = 5.6 Hz, CHOTBS), 3.57 (1H, dd, J =
10.4, 6.8 Hz, CHAHBOH), 3.47 (1H, dd, J = 10.8, 5.2 Hz, CHAHBOH), 2.01 (1H, br s,
OH), 1.89-1.80 (1H, m, CH(CH3)CH2OH), 1.70 (3H, s, CH2C(CH3)CHOTBS), 0.90
(9H, s, OSiC(CH3)3), 0.86 (3H, d, J = 6.8Hz, CH(CH3)CH2OH), 0.06 (3H, s,
13
OSi(CH3)CH3), 0.00 (3H, s, OSi(CH3)CH3); C NMR (100 MHz, CDCl3) δ 146.6,
112.1, 78.3, 66.0, 39.7, 26.0, 18.8, 18.3, 12.1, -4.5, -5.1.
O
O
TBS
12
(2R,3R)-3-(tert-butyldimethylsilyloxy)-2,4-dimethyl-pent-4-enal (12).3
o
To a stirred solution of DMSO (1.02 mL; 14.3 mmol) in CH2Cl2 (48 mL) at -78 C
was added (COCl)2 (3.58 mL; 2 M in CH2Cl2; 7.16 mmol) dropwise and the resulting
o
solution was stirred at -78 C for 30 min. Alcohol 44 (1.17 g; 4.77 mmol) was added
o
dropwise via cannula (CH2Cl2, 8 mL) and the mixture stirred at -78 C for 45 min
before Et3N Et3N (3.99 mL; 28.6 mmol) was added dropwise. The mixture was stirred
at -78 oC for a further 30 min before warming to 0 oC for 30 min and the reaction was
quenched by addition of sat. aq. NH4Cl (120 mL). The product was extracted with
CH2Cl2 (3 x 40 mL), the combined organic extracts dried (Na2SO4) and
concentratrated in vacuo. Purification by column chromatography (buffered silica,
100% CH2Cl2) gave aldehyde 12 as a colourless oil. Rf = 0.40 (100% CH2Cl2); [α]20
D
1
= +32.9 (c 1.10, CH2Cl2); H NMR (400 MHz, CDCl3) δ 9.69 (1H, d, J = 1.6 Hz,
CHO), 4.97 (1H, m, CHAHBC(CH3)CHOH), 4.91 (1H, m, CHAHBC(CH3)CHOH),
4.40 (1H, d, J = 4.8 Hz, CHOTBS), 2.47 (1H, ddq, J = 6.8, 4.8, 1.6, CH(CH3)CHO),
1.68 (3H, s, CH2C(CH3)CHOTBS), 1.04 (3H, d, J = 6.8 Hz, CH(CH3)CHO), 0.87
13
(9H, s, OSiC(CH3)3), 0.03 (3H, s, OSi(CH3)CH3), 0.00 (3H, s, OSi(CH3)CH3); C
NMR (100 MHz, CDCl3) δ 204.7, 115.0, 113.1, 76.0, 53.6, 50.7, 25.9, 18.6, 8.5, -4.4,
-5.1.
7

Supplementary Information for “Stereoselectivity of model C22-23 aldol coupling for spirangiens A &
B” by Claire Gregg and Michael V. Perkins
References:
1 Walkup, R. D.; Boatman Jr., P. D.; Kane, R. R.; Cunningham, R. T. Tetrahedron
Lett. 1991, 32, 3937–3940
2 (i) Mulzer, J., Hanbauer, M. Tetrahedron Lett. 2000, 41, 33-36. (ii) Ahmed, A.,
Hoegnauer, E. K., Enev, V. S., Hanbauer, M., Kaehlig, H., Ohler, E., Mulzer, J. J.
Org. Chem. 2003, 68, 3026-3042.
3 (i) Smith, A. B., Barbosa, J., Wong, W., Wood, J. L. J. Am. Chem. Soc. 1995, 117,
10777-10778. (ii) Smith, A. B., Barbosa, J., Wong, W., Wood, J. L. J. Am. Chem.
Soc. 1996, 118, 8316-8328.
8

Supplementary Information for “Stereoselectivity of model C22-23 aldol coupling for spirangiens A & B” by Claire Gregg and Michael V. Perkins
TBSO
O
OPMB
3
400 MHz, CDCl3
9

Supplementary Information for “Stereoselectivity of model C22-23 aldol coupling for spirangiens A & B” by Claire Gregg and Michael V. Perkins
TBSO
O
OPMB
3
100 MHz, CDCl3
10

Supplementary Information for “Stereoselectivity of model C22-23 aldol coupling for spirangiens A & B” by Claire Gregg and Michael V. Perkins
O
O
O
4
400 MHz, CDCl3
11

Supplementary Information for “Stereoselectivity of model C22-23 aldol coupling for spirangiens A & B” by Claire Gregg and Michael V. Perkins
O
O
O
4
100 MHz, CDCl3
12

Supplementary Information for “Stereoselectivity of model C22-23 aldol coupling for spirangiens A & B” by Claire Gregg and Michael V. Perkins
O
O
TBS TES
O
5
400 MHz, CDCl3
13

Supplementary Information for “Stereoselectivity of model C22-23 aldol coupling for spirangiens A & B” by Claire Gregg and Michael V. Perkins
O
O
TBS TES
O
5
100 MHz, CDCl3
14

Supplementary Information for “Stereoselectivity of model C22-23 aldol coupling for spirangiens A & B” by Claire Gregg and Michael V. Perkins
H
O
OH
O
23
O
23
OH
19
OH OH OH
OTBS
TBSO
18
OH
600 MHz, CDCl3
15

Supplementary Information for “Stereoselectivity of model C22-23 aldol coupling for spirangiens A & B” by Claire Gregg and Michael V. Perkins
H
O
OH
O
23
O
23
OH
19
OH OH OH
OTBS
TBSO
18
OH
COSY, 600 MHz, CDCl3
16

Supplementary Information for “Stereoselectivity of model C22-23 aldol coupling for spirangiens A & B” by Claire Gregg and Michael V. Perkins
H
O
OH
O
23
O
23
OH
OH OH OH
OTBS
TBSO
18
19
NOESY, 600 MHz, CDCl3
OH
17

Supplementary Information for “Stereoselectivity of model C22-23 aldol coupling for spirangiens A & B” by Claire Gregg and Michael V. Perkins
OTBS
O
OH OH
TBS
O
OPMB
22
OTBS
OH
O
21
O
OPMB
TBS
21
OH
600 MHz, CDCl3
18

Supplementary Information for “Stereoselectivity of model C22-23 aldol coupling for spirangiens A & B” by Claire Gregg and Michael V. Perkins
OTBS
O
OH OH
TBS
O
OPMB
22
OTBS
OH
O
21
O
OPMB
TBS
21
OH
COSY, 600 MHz, CDCl3
19

Supplementary Information for “Stereoselectivity of model C22-23 aldol coupling for spirangiens A & B” by Claire Gregg and Michael V. Perkins
TBS
O
TBSO
O
OH
O
21
O
OPMB
O
OH OH
TBS
OPMB
TBS
21
22
OH
NOESY, 600 MHz, CDCl3
20

Supplementary Information for “Stereoselectivity of model C22-23 aldol coupling for spirangiens A & B” by Claire Gregg and Michael V. Perkins
TBSO
O
OH OH
TBS
O
OPMB
23
TBS
O
OH
O
O
OPMB
TBS
24
OH
600 MHz, CDCl3
21

Supplementary Information for “Stereoselectivity of model C22-23 aldol coupling for spirangiens A & B” by Claire Gregg and Michael V. Perkins
TBSO
O
OH OH
TBS
O
OPMB
23
TBS
O
OH
O
O
OPMB
TBS
24
OH
COSY, 600 MHz, CDCl3
22

Supplementary Information for “Stereoselectivity of model C22-23 aldol coupling for spirangiens A & B” by Claire Gregg and Michael V. Perkins
TBS
O
TBSO
O
OH
O
O
OPMB
O
OH OH
TBS
OPMB
TBS
24
23
OH
NOESY, 600 MHz, CDCl3
23