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. Author manuscript; available in PMC: 2008 Dec 8.
Published in final edited form as: J Nat Prod. 2007 Jul 4;70(7):1073–1083. doi: 10.1021/np0680735

Scheme 3.

Scheme 3

a

aReagents and conditions: (a) (i) Oxalyl chloride, catalytic DMF, DCM, 0-23 °C, 2h. (ii) 19, pyridine, 23°C, 16 h, 75%. (b) LiI, pyridine, 110°C, 40 h, 89%. (c) (i) 7, 1:1 TFA-DCM, 0.5 h. (ii) PyBroP, DIPEA, DCM, product from (i), 4 h, 65%. (d) BF3·Et2O, DCM, 0.5 h, 87% for 23, 83% for 27-28. (e) 25, MNBA, DMAP, TEA, DCM, 23 °C, 16 h, 77%.