Biomedical Engineering Reference
In-Depth Information
OH
OH
OH
HO
OH
OH
40°C, 100 min
90
OMe
NH
2
OH
CH(OMe)
3
, CSA
O
O
MeOH
2
100 psi bpr
OMe
91
(55%)
O
O
(1.8 equiv)
SCHEME 11.17
Flow synthesis of BDA-protected glyceraldehyde
91
.
simple silica-based column chromatography step was found beneficial to obtain
analytically pure
.
The subsequent aldehyde
91
were then readily obtained from the
hemiacetal produced using a recycling procedure through a resin-bound periodate.
The aldehyde
93
and ester
95
was obtained following passage through a short plug of magnesium
sulfate to remove any residual water (Scheme 11.18).
Similarly, the analogous methyl ester
93
under oxidizing
conditions via oxidation of the
in situ
-generated aldehyde intermediate using an
immobilized perbromide resin (Scheme 11.19).
Finally, the BDA-protected glycolate
95
was formed from
91
, a useful building block, was syn-
thesized using related procedures (Scheme 11.22). Here, using conditions similar to
the tartrate protection reaction described above, chloropropanediol
100
96
was converted
to
in 95% yield, without any substrate racemization being observed. Also, since
this conversion proceeded so efficiently, it was not necessary to use the periodate
cleavage protocol to remove excess diol
96
(Scheme 11.20).
Chloride
97
, which was formed as a single product, was then subjected to a
strong base to effect elimination to give the
exo
alkene
97
. Unfortunately, owing to
the ease of isomerization of the double bond, it was not possible to scavenge all the
excess base with an immobilized acid, and instead the product streamwas collected
into a flask containing water and extracted in a typical batch fashion
(Scheme 11.21).
98
OMe
OMe
OH
NMe
3
IO
4
MgSO
4
O
O
O
O
O
H
2
100 psi bpr
91
OMe
OMe
93
(90%)
CH
2
Cl
2
/H
2
O (9:1)
recycle
0.5 mL/min, 14 h
SCHEME 11.18
Corresponding aldehyde (
93
) of BDA-protected glyceraldehyde.
NH Br
3
OMe
OMe
OH
NMe
3
IO
4
O
O
O
O
O
MeO
2
100 psi bpr
100 psi bpr
OMe
OMe
95
(86%)
94
MeOH
recycle
0.5 mL/min, 14 h
SCHEME 11.19
Corresponding ester (
95
) of BDA-protected glyceraldehyde.
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