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Named reactions

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Search synthesis

Cyanocobalamin

This famous synthesis was achieved through a collaboration between the research groups of Rober B. Woodward and of Albert Eschemoser. It took a team of about a hundred co-workers working for over a decade to perform the complete synthesis.

Chemical structure of Cyanocobalamin
C63H89CoN14O14P
Author Robert B. Woodward
Publication year 1973
Synthesis type Formal synthesis
Number of steps 72 (7 parts)
References

Browse hundreds of other total syntheses.

Part 1 of 7
Chemical structure
+
Chemical structure
H3PO4
80 °C, 82 %

See the Claisen-Schmidt Condensation
Chemical structure
+
Chemical structure
SnCl4
PhH
RT, 73 %

See the Diels-Alder Reaction
The enantiomers were resolved with (+)- and (-)-phenylethylamine.
Chemical structure
CrO3, H2SO4
Acetone
RT, 75 %
Chemical structure
SOCl2
77 °C
Chemical structure
CH2N2
Et2O, Dioxane
RT
Chemical structure
Ag2O
MeOH
65 °C, 69 % (3 steps)

See the Wolff Rearrangement
Chemical structure
NH3
MeOH
RT, 55 %
Chemical structure
P2S5
THF
RT, 85 %
Chemical structure

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Part 2 of 7
Chemical structure
CH2N2, NaOMe
Et2O, MeOH
92 %
Chemical structure
H2S
CF3CO2H
RT, 78 %
Chemical structure
(Ph3P)3RhCl
PhMe
110 °C, 30 %
Chemical structure

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Part 3 of 7
Chemical structure
+
Chemical structure
Bz2O, HCl
CH2Cl2
RT
Chemical structure
P(OEt)3
Xylene(s)
125 °C, 85 % (2 steps)

See the Eschenmoser Sulfide Contraction
Chemical structure
P2S5, 4-Methylpyridine
Xylene(s)
130 °C, 84 %
Chemical structure

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Part 4 of 7
Chemical structure
MeMgI, Propargyl bromide
Chemical structure
HgO, BF3.OEt2
MeOH

See the Kucherov Reaction
See the Mannich Reaction
Chemical structure
+
Chemical structure
"the diastereomeric ureas resulting from the combination of the racemic tricyclic ketone with optically active alpha-phenylethylisocyanate are very readily separable"
Chemical structure
"and are readily re-converted to the parent active tricyclic ketones when pyrolyzed"
Chemical structure

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Part 5 of 7
Chemical structure
No experimental details were reported for this whole part.
Chemical structure
Chemical structure
Chemical structure
Chemical structure
Chemical structure
Chemical structure
LiAlH4
Chemical structure
CrO3
Chemical structure
+
Chemical structure
Chemical structure
Chemical structure
Chemical structure

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Part 6 of 7
Chemical structure
+
Chemical structure
Chemical structure
KOt-Bu
t-BuOH

See the Michael Addition
Chemical structure
(CH2OH)2, TsOH
PhH
Chemical structure
Et3O+ BF4-
Chemical structure
MeOH
Chemical structure
PhMe
Reflux
Chemical structure
Li, NH3
THF, THF

See the Birch Reduction
Chemical structure
90 %

"When subjected to acid treatment under carefully controlled condition"
Chemical structure
"further treated with acid"
Chemical structure
NH2OH
Chemical structure
NaNO2
AcOH
Chemical structure
O3, HIO4
MeOH
Chemical structure
CH2N2
Et2O
Chemical structure
Pyrrolidinium acetate
MeOH

See the Aldol Condensation
Chemical structure
MsCl, Et3N
Chemical structure
O3, HIO4
EtOAc, H2O
Chemical structure
CH2N2
Et2O
Chemical structure
Polystyrenesulfonic acid
MeOH
170 °C

See the Beckmann Rearrangement
Also isolated was the C3-epimer which was equilibrated to the desired product.
Chemical structure
PhSH, HCl
MeOH
Chemical structure
O3
Chemical structure
NH3
Chemical structure
NaBH4
Chemical structure
Ms2O
Chemical structure
LiBr
DMF

See the Finkelstein Reaction
Chemical structure

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Part 7 of 7
Chemical structure
+
Chemical structure
KOt-Bu
100 %
Chemical structure
P(CH2CH2CN)3
CF3CO2H, MeNO2

See the Eschenmoser Sulfide Contraction
Chemical structure
P2S5, 4-Methylpyridine
PhMe
Chemical structure
Me2NH
Chemical structure
ZnCl2
Chemical structure
I2
MeOH
Chemical structure
"it was a relatively easy matter to remove the zinc by treatment with acid"
Chemical structure
Ph3P
CF3CO2H, CH2Cl2

See the Eschenmoser Sulfide Contraction
Chemical structure
CoCl2
THF
Chemical structure
NaCN
Chemical structure
I2
AcOH
Chemical structure
BnOCH2Cl
Sulfolane
75-80 °C

See the Blanc Halomethylation
Chemical structure
PhSH
Chemical structure
Ni (Raney)
Chemical structure
CH2N2
Et2O
Chemical structure
H2SO4
H2O
60 min

Also isolated was the C13-epimer in an unfavorable 28:72 ratio.
Chemical structure
N2O4, NaOAc
CCl4
0 °C, 60 min, 70-80 %
Chemical structure
NH3, NH4Cl
Ethylene Glycol
75 °C, 10 h, 100 %
Chemical structure

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Remaining...
(1 step)

See: Helv. Chim. Acta 1960 , 43, 704.
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