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. Author manuscript; available in PMC: 2012 Aug 7.
Published in final edited form as: Tetrahedron. 2011 Oct 29;67(52):10249–10260. doi: 10.1016/j.tet.2011.10.026

Scheme 10.

Scheme 10

A-Ring functionalization: Installation of C2 and C3 stereocenters.

Key: a) L-Selectride; then 37, 62%, 1.25:1 dr; b) n-Bu4NN3, THF; c) HOAc, NaBH3(CN), CH2Cl2; d) NaBH4, CeCl3•7H2O, 42% from 38a; e) Boc2O, NaOH, THF/H2O (43a); f) Fmoc-OSu, Na2CO3, THF/H2O (44a); g) L-Selectride, −78 °C, 80%; h) LiHMDS, then 37, −78 °C, 73%, 1:1 dr; i) NaN3, DMF; then NaBH(OAc)3, HOAc, (HCHO)X, 50 °C, 69%; j) NaBH(OAc)3, HOAc, CH2Cl2; k) DIBAL-H, −78 °C, < 20% from 40b.