Efficient chemical conversion of louisianin A to C and D, the inhibitor of angiogenesis

Louisianin A (1) was treated with phosphoryl chloride (POC13) at 120~ 125°C3) to obtain chloro derivative (2) in 86% yield. 2 was reduced by Zn-AcOH at 50°C4) to afford 3 (52% yield) and 4 (35% yield). Furthermore, under the same condition, 3 was dechlorinated to give 4 in 48% yield. Moreover, 4 was oxidized in the treatment of CrO3-pyridine5) to obtain louisianin C (5) in 75% yield. Finally, 5 was treated with 1,8-diazabicyclo[5,4,0]-undec-7-ene (DBU) in benzene at 85°C6) to obtain louisianin D (6) in 84% yield. (Scheme 1) In summary, the efficient conversion of louisianin A (1) to C (5) (51% overall yield, based on 3 recovered), and D (6) (43% overall yield, based on 3 recovered) enables us to prepare additional quantities of louisianin C (5), and D (6) to clarify their biological activity.