Notes
J . Org. Chem., Vol. 63, No. 11, 1998 3789
desired benzoate 9 was isolated as a white solid (5.33 g, 86%,
mp 155 °C): 1H NMR (200 MHz, CDCl3) δ 0.70-0.85 (m, 12H),
1.04 (d, J ) 6.5 Hz, 3H), 1.09 (s, 3H), 4.92-5.24 (m, 3H), 7.40-
7.63 (m, 3H), 7.99-8.04 (m, 2H); 13C NMR (50.3 MHz, CDCl3) δ
10.3, 11.7, 12.0, 18.7, 20.9, 21.0, 23.5 25.1, 28.5, 31.6, 33.3, 35.4,
37.8, 38.0, 38.3, 39.0, 40.1, 40.3 42.3, 43.6, 46.8, 50.4, 50.9, 55.5,
71.0, 128.2, 129.2, 129.3, 130.4, 132.7, 137.8, 165.3, 210.8; MS
(FD) 532. Anal. Calcd for C36H52O3: C, 81.15; H, 9.84. Found:
C, 80.98; H, 9.89.
7r-Ben zyloxy-3-d ioxola n e-5,6-d ih yd r ostigm a ster ol (10).
Steroid 9 (4.0 g, 7.5 mmol) was dissolved in toluene (250 mL) in
a 500 mL round-bottom flask. p-Toluenesulfonic acid (250 mg)
and ethylene glycol (5 mL, large excess) were added. The flask
was equipped with a Dean-Stark trap, and the reaction was
brought to reflux. The reaction was refluxed for 2 h before being
allowed to cool. The reaction was treated with approximately 2
g of anhydrous sodium carbonate, followed by water. The
organic layer was washed (2×) with sodium bicarbonate, deion-
ized water, and brine and dried over Na2SO4. The solvent was
removed by rotory evaporation to yield the ketal 10 (4.1 g, 7.1
mmol, 95%, mp 74 °C) as a light yellow waxy solid: 1H NMR
(200 MHz, CDCl3) δ 0.70-0.81 (m, 12H), 0.89 (s, 3H), 1.01 (d, J
) 6.5 Hz, 3H), 3.87 (sharp m, 4H), 4.92-5.23 (m, 3H), 7.40-
7.63 (m, 3H), 8.04-8.14 (m, 2H); 13C NMR (50.3 MHz, CDCl3) δ
10.4, 11.8, 12.1, 18.8, 21.0, 23.6, 25.3, 28.7, 31.1, 31.7, 33.1, 35.4,
35.6, 37.1, 37.2, 38.5, 39.3, 40.4, 42.5, 47.1, 50.7, 51.1, 55.6, 64.0,
71.8, 108.9, 128.3, 129.2, 129.5, 130.9, 132.6, 138.0, 165.8; MS
(FD) 576. Anal. Calcd for C38H56O4: C, 79.12; H, 9.78. Found:
C, 78.89; H, 9.75.
7r-Ben zyloxy-3-d ioxola n e Ch olesta n -22-a l (11). Sterol 10
(3.5 g, 6.1 mmol) was dissolved in methylene chloride/ethanol
(250 mL of 2/1). The Welsbach ozonolyzer was purged with
oxygen at 7 psi, 1 mL/min, and the water was turned on. The
sterol solution was then chilled in a dry ice/ethanol bath. The
ozonolyzer was set at 90 V and switched on. Ozone was bubbled
into the magnetically stirred, chilled flask until a blue coloration
was observed. The power was switched off, and oxygen was
bubbled into the flask until the color dissipated. Trimethyl
phosphite (5 mL) was added to the reaction vessel. The ice bath
was removed and the reaction mixture was allowed to warm to
room temperature. The solvent was removed by rotory evapora-
tion and the flask was placed under high vacuum overnight to
remove any remaining trimethyl phosphate. The resulting white
solid was chromatographed on silica gel, eluting with a gradient
of ethyl acetate in toluene, to give the desired product 11 (2.7 g,
5.5 mmol, 90%, mp 166-168 °C) as a white solid: 1H NMR (400
MHz, CDCl3) δ 9.52 (d, J ) 2.4 Hz, 1H), 8.06 (d, J ) 7 Hz, 2H),
7.60 (t, J ) 7 Hz, 1H), 7.49 (t, J ) 7 Hz, 2H), 5.17 (m, 1H), 3.88
(m, 4H), 2.35 (m, 1H), 2.0-1.1 (m, 21H), 1.11 (d, J ) 6.9 Hz,
3H), 0.89 (s, 3H), 0.73 (s, 3H); 13C NMR (50.3 MHz, CDCl3) δ
10.4, 12.0, 13.3, 20.9, 23.8, 26.7, 31.1, 33.1, 35.3, 35.5, 37.0, 37.1,
38.4, 39.0, 43.2, 47.1, 49.3, 49.9, 50.7, 64.0, 71.6, 108.8, 128.3,
129.5, 130.7, 132.7, 165.8, 204.8.
7r-Ben zyloxy-3-d ioxola n e 24-Ketoch olest-22-en e (13). A
solution of 1-bromo-3-methyl-2-butanone11 (10 g, 60 mmol) and
triethyl phosphite (10.3 mL, 60 mmol) was heated to 120 °C
under nitrogen for 3 h with the removal of ethyl bromide by
distillation. The cooled reaction mixture was placed under high
vacuum and then distilled to afford diethylphosphono-3-methyl-
2-butanone (12, 8.0 g, 60%, bp 127-130 °C, 3 mm):12 1H NMR
(400 MHz, CDCl3) δ 4.15 (p, J ) 7 Hz, 4H), 3.14 (d, J ) 22.5 Hz,
2H), 2.87 (heptet, 7 Hz, 1H), 1.34 (t, J ) 7 Hz, 6H), 1.13 (d, J )
7 Hz, 6H).
mmol, 90%, mp 85-121 °C): 1H NMR (400 MHz, CDCl3) δ 8.06
(d, J ) 7.4 Hz, 2H), 7.59 (t, J ) 7.1 Hz, 1H), 7.48 (t, J ) 7.4 Hz,
2H), 6.65 (d of d, J ) 15.6 and 9 Hz, 1H), 6.02 (d, J ) 15.6 Hz,
1H), 5.15 (br s, 1H), 3.88 (br s, 4H), 2.80 (hept, J ) 6.7 Hz, 1H),
2.25 (m, 1H), 2.0-1.0 (m, 21H), 1.08 (d, 3H), 1.06 (d, J ) 6.9
Hz, 6H), 0.89 (s, 3H), 0.72 (s, 3H); 13C NMR (400 MHz, CDCl3)
δ 11.0, 12.5, 13.9, 18.9, 19.1, 19.8, 21.5, 24.1, 28.5, 31.7, 33.7,
36.0, 36.2, 37.7, 37.8, 38.7, 39.1, 39.8, 40.4, 43.5, 47.7, 51.1, 55.3,
64.6, 64.7, 72.3, 109.5, 126.8, 128.9, 130.1, 131.4, 133.3, 152.8,
166.4, 205.0; MS (+FAB) 563.3 (M + 1). Anal. Calcd for
C36H50O5‚0.2H2O: C, 76.34; H, 8.97. Found: C, 76.26; H, 9.13.
7r-Ben zyloxy-3-d ioxola n e Ch olest-22-en -24(R)-ol (14).
An argon-blanketed flask was charged with 1 M R-MeCBS in
toluene (0.92 mL, 0.92 mmol) and 1 M borane-THF complex in
THF (2.3 mL, 2.3 mmol). The reaction mixture was stirred at
room temperature for 2 h, cooled to -20 °C, and treated with a
solution of 13 (520 mg, 0.92 mmol) in anhydrous toluene (15
mL) over 1.5 h. After 1 h, the reaction mixture was treated with
solid ammonium chloride and water (2 mL), warmed to room
temperature, diluted with more water (20 mL), and extracted
into toluene (2 × 80 mL). The toluene layer was washed with
saturated ammonium chloride (3 × 50 mL), dried with magne-
sium sulfate, and evaporated to give a solid, which was recrys-
tallized from ethyl acetate in hexane to give 14 in two crops (491
mg, 0.87 mmol, 94%, mp 196-199 °C, 91% de): 1H NMR (400
MHz, CDCl3) δ 8.06 (d, J ) 7 Hz, 2H), 7.59 (t, J ) 7 Hz, 1H),
7.48 (t, J ) 7 Hz, 2H), 5.35 (m, 2H), 5.16 (br s, 1H), 3.88 (br s,
4H), 3.67 (t, J ) 6.2, 1H), 2.1-1.0 (m, 23H), 1.03 (d, J ) 6.3 Hz,
3H), 0.89 (m, 6H), 0.82 (d, J ) 6.6 Hz, 3H), 0.70 (s, 3H); 13C
NMR (400 MHz, CDCl3) δ 10.7, 12.2, 18.4, 18.6, 20.6, 21.3, 23.9,
28.8, 31.5, 33.5, 34.1, 35.7, 35.9, 37.4, 37.5, 38.8, 39.6, 40.2, 42.9,
47.4, 51.0, 55.6, 64.3, 64.4, 72.0, 78.8, 109.2, 128.6, 128.8, 129.9,
131.2, 133.0, 139.8, 166.1,; MS (+FAB) 565.3 (M + 1). Anal.
Calcd for C36H52O5-0.2H2O: C, 76.07; H, 9.29. Found: C, 75.93;
H, 9.14.
7r-Ben zyloxy-3-d ioxola n e Ch olesta n -24(R)-ol (4). A so-
lution of 14 (2.7 g, 4.8 mmol) in THF (30 mL) was treated with
sodium nitrite (89 mg, 1.3 mmol), 20% palladium hydroxide on
carbon (0.5 g, Pearlman’s catalyst), and 40 psi of hydrogen in a
Parr apparatus. After 16 h, the reaction mixture was filtered
through Celite and concentrated to obtain crude material, which
was recrystallized from dichloromethane in hexane (15 mL) to
afford pure 4 (2.13 g, 3.76 mmol, 78%, mp 205-208 °C): 1H NMR
(400 MHz, CDCl3) δ 8.08 (d, J ) 7.5 Hz, 2H), 7.60 (t, J ) 7.5
Hz, 1H), 7.49 (t, J ) 7.5 Hz, 2H), 5.16 (br s, 1H), 3.88 (m, 4H),
3.28 (m, 1H), 2.0-1.0 (m, 27H), 0.93-0.90 (m, 9H), 0.89 (s, 3H),
0.69 (s, 3H); 13C NMR (400 MHz, CDCl3) δ 11.0, 12.2, 17.7, 19.1,
19.4, 21.5, 24.1, 28.5, 31.0, 31.7, 32.4, 33.7, 33.9, 35.9, 36.1, 37.6,
37.8, 39.0, 39.9, 43.2, 47.6, 51.1, 56.3, 64.6, 64.7, 72.4, 77.3, 109.5,
128.9, 130.2, 131.5, 133.3, 166.5; MS (+FAB) 567.5 (M + 1). Anal.
Calcd for C36H54O5-0.3H2O: C, 75.56; H, 9.62. Found: C, 75.29;
H, 9.04.
Ack n ow led gm en t. The authors would like to thank
Rudolph Kullnig for the X-ray diffraction study; and
Ze′ev Shaked, Harold Meckler, Aline Total, J ean Las-
tennet, Ronald S. Michalak, Ming-Teh Lin, Alexander
Weis, Ivan Alferiev, and Peech Reddy for their contribu-
tions to the synthesis of squalamine intermediate 4.
Sodium hydride (60%, 44 mg, 1.1 mmol) was washed with
heptane (2 mL) and hexane (2 × 2 mL) and evaporated with a
nitrogen flow. Anhydrous THF (2 mL), diethylphosphono-3-
methyl-2-butanone (12, 0.34 mL, 1.5 mmol), and a solution of
11 (486 mg, 0.982 mmol) in THF (3 mL) were added. The
reaction mixture was heated to reflux for 1 h, cooled to room
temperature, and treated with water (25 mL). The aqueous
layer was extracted with ethyl acetate (3 × 50 mL), which was
in turn washed with brine (3 × 50 mL) and water (2 × 50 mL)
and dried over sodium sulfate. After removal of the solvent, the
product was dissolved in methanol (5 mL) containing 4 drops of
pyridine and dropped into water (100 mL) with shaking. The
resulting solid was filtered, washed with water (3 × 20 mL),
and dried under vacuum at 50 °C to give pure 13 (499 mg, 0.89
Su p p or tin g In for m a tion Ava ila ble: X-ray information
for compound 4 (13 pages). This material is contained in
libraries on microfiche, immediately follows this article in the
microfilm version of the journal, and can be ordered from the
ACS; see any current masthead page for ordering information.
J O971405D