Exo- and diastereo- selective syntheses of himbacine analogs

A process for preparing Compound 1:

• said process comprising the steps of:
• (a) cyclizing Compound 2 in a first solvent at an elevated temperature
• where R5 and R6 are each independently selected from the group consisting of II, alkyl, alkenyl, alkynyl, alkoxy, cycloalkyl, aryl, alkylaryl, arylalkyl, heterocyclic and heteroaryl groups, or R5 and R6, together with the nitrogen to which they are attached, for a 3- to 6-membered heterocyclic compound containing 1-4 heteroatoms,
• to produce a first mixture of exo isomers
• said isomers having a trans-[5,6]-ring junction:
• and endo isomers:
• (b) epimerizing said trans-[5,6]-ring-junction in Compound 29 by treating said first mixture with a first base to produce a second mixture comprising cis-[5,6]-ring-junction-nitro-α isomer and cis-[5,6]-ring-junction-nitro-β isomer of Compound 30:
• and
• (c) treating said second mixture with a second solvent, causing said α-isomer of Compound 30 to precipitate to produce Compound 1.