Synthetic methods and intermediates for the preparation of xenicanes

A compound of formula 1:

• wherein:
• Ra is H, (C1-C6)alkyl, (C2-C6)alkenyl, (C2-C6)alkynyl, (C3-C8)cycloalkyl, (C3-C8)cycloalkyl(C1-C6)alkyl, aryl, or heteroaryl, wherein each (C1-C6)alkyl, (C2-C6)alkenyl, (C2-C6)alkynyl, (C3-C8)cycloalkyl, and (C3-C8)cycloalkyl(C1-C6)alkyl of Ra is optionally substituted with one or more groups independently selected from halo, hydroxy, cyano, nitro, (C1-C6)alkoxy, (C3-C8)cycloalkyl, oxo, carboxy, aryl, aryloxy, and —NRbRc;
• and wherein each aryl, and heteroaryl of Ra is optionally substituted with one or more groups independently selected from (C1-C6)alkyl, halo, hydroxy, cyano, carboxy, nitro, trifluoromethyl, trifluoromethoxy, (C1-C6)alkoxy, (C1-C6)alkoxycarbonyl, (C1-C6)alkanoyloxy, and —NRbRc;
• and
• Rb and Rc are each independently selected from H, (C1-C6)alkyl, (C3-C8)cycloalkyl, (C3-C8)cycloalkyl(C1-C6)alkyl, aryl, heteroaryl, aryl(C1-C6) alkyl and heteroaryl(C1-C6)alkyl;
• or Rb and Rc together with the nitrogen to which they are attached form a aziridino, azetidino, morpholino, piperazino, pyrrolidino or piperidino.