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A mixture of 1.05 g of aminoguanidine hydrogencarbonate in 23 ml of water and 70 ml of dioxane was made acid to pH 3 with 3N HCl. A solution of 2.08 g of (E)-3β,14β-dihydroxy-5β-pregn-20-ene-21-carboxaldehyde (Fullerton D. S. et al., J. Med. Chem., 1976, 19, 1330) in 20 ml of dioxane was added at room temperature. After 3 days the mixture was evaporated to dryness under reduced pressure. The crude product was purified by flash chromatography (SiO2) using chloroform/methanol/28% ammonium hydroxide 80/20/3 as the eluant; the fractions containing the title compound were collected and evaporated to dryness. The residue was ground with diethyl ether and ethanol to give 1.58 g of the title compound (I-aa) as a white solid.

1. customAfter 3 days the mixture was evaporated to dryness under reduced pressure
2. customThe crude product was purified by flash chromatography (SiO2)
3. additionthe fractions containing the title compound
4. customwere collected
5. customevaporated to dryness