+++ Tetrahedron Lett.

[bobchandra]

Progress toward the total synthesis of maytansinoids. An efficient route to two major precursors (western-southern zone)
A.I. Meyers, Kiyoshi Tomioka, Dennis M. Roland, Daniel Comins
Tetrahedron Letters
Volume 19, Issue 16, 1978, Pages 1375–1378

DOI:

http://dx.doi.org/10.1016/S0040-4039(01)94549-6

Thank you!