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0 °C

To the solution of lithium borohydride (0.305 g, 13 mmol) in anhydrous tetrahydrofuran (25 mL) was added a solution of ethyl ester 73 (2.69 g, 9.2 mmol) in THF (25 mL) over a period of 30 mins at 0° C. After the addition the reaction mixture was brought to room temperature and stirred further under argon. The completion of the reaction was ascertained by TLC after 4 h. (Rf=0.3 in 10% MeOH/CHCl3). The reaction mixture was evaporated to dryness and cooled to 0° C. To the residue 3N HCl (40 mL) was added slowly. After stirring for 30 mins the product was extracted with dichloromethane (3×75 mL). The combined organic layer was washed with brine and dried over sodium sulfate. Organic layer was filtered and evaporated to dryness. Compound 74 was purified by column chromatography first by eluting with dichloromethane/methanol (5%) (1.98 g, 85%).

1. additionAfter the addition the reaction mixture
2. customwas brought to room temperature
3. customThe reaction mixture was evaporated to dryness
4. additionTo the residue 3N HCl (40 mL) was added slowly
5. stirringAfter stirring for 30 mins the product
6. extractionwas extracted with dichloromethane (3×75 mL)
7. washThe combined organic layer was washed with brine
8. dry with materialdried over sodium sulfate
9. filtrationOrganic layer was filtered
10. customevaporated to dryness
11. customCompound 74 was purified by column chromatography first
12. washby eluting with dichloromethane/methanol (5%) (1.98 g, 85%)