Synthesis of Cylindrospermopsin

C15H21N5O7S

Principal investigator	Barry B. Snider
Publication year	2000
Synthesis type	Total
Number of steps	24 (3 parts)
References	J. Am. Chem. Soc. 2000, 122, 5017.

Part 1 of 3

POCl3, PCl5

Reflux, 2 d

MeOH

0 °C to RT, 12 h, 57% (2 steps)

LiBH4

EtOH, THF

RT, 2 h, 93%

Dess-Martin Periodinane

CH2Cl2

RT, 60 min, 90%

See the Dess-Martin Oxidation

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Part 2 of 3

ClCO2CH2CCl3

THF

-30 °C, 2.5 h, 49%

"The yield was 87 % brsm."

CuBr.Me2S , VinylMgBr
TMSCl

THF

-78 °C, 2 h, 92%

See the Michael Addition

AcOH, CH2Cl2

RT, 5 h, 96%

Li(s-Bu)3BH

THF

-78 °C, 2 h, 94%

ClCO2Bn, Na2CO3

THF

RT, ON, 96%

Imidazole, DMAP, TBSCl

CH2Cl2

RT, ON, 89%

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Part 3 of 3

EtMgBr

																	THF															

								0 °C to RT, 								4 h, 								69%
							
								See the Grignard Reaction
							
								"The yield was 83 % brsm."

Imidazole, TBSCl

CH2Cl2

RT, 5 h, 88%

O3
Me2S

CH2Cl2

-78 °C, 20 min, 72%

BnNH2, Na2SO4, NaBH3CN

AcOH, MeOH, PhMe

RT, 4 h, 68%

H2, Pd/C

1 atm

MeOH

RT, ON

BrCN

PhMe

RT, 5 h

ClCO2Bn, NaH

THF

0 °C to RT, 8 h, 45% (3 steps)

n-Bu4N+ F-

THF

RT, ON, 83%

MnO2

CH2Cl2

RT, 60 min, 87%

Ac2O

Pyr

RT, ON, 87%

CuBr2

EtOAc

35 °C, 20 min

H2, Pd(OH)2/C

1 atm

MeOH

RT, 8 h, 42% (2 steps)

"Also isolated was the C7-epimer (28 % yield)."

HCl

H2O

100 °C, 6 h, 95%

Na2SO4, SO3.DMF

Pyr

RT, ON, 50-70%

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