for illustrative purposes only and are not intended nor should they be construed as limiting the invention in any manner those skilled in the art will appreciate that variations and modifications of the following examples can be made without exceeding the spirit or scope of the invention as will be evident to those skilled in the art individual diastereoisomeric forms can be obtained by separation of mixtures thereof in conventional manner for example chromatographic separation may be employed compound names were generated with acdlabs version 12 5 and intermediates and reagent names used in the examples were generated with software such as chem bio draw ultra version 12 0 or auto nom 2000 from mdl isis draw 2 5 sp1 in general characterization of the compounds is performed according to the following methods proton nuclear magnetic resonance 1 h nmr and carbon nuclear magnetic resonance 13 c nmr spectra were recorded on a varian 300 or 600 mhz spectrometer in deuterated solvent chemical shifts were reported as u03b4 delta values in parts per million ppm relative to tetramethylsilane tms as an internal standard 0 00 ppm and multiplicities were reported as s singlet d doublet t triplet q quartet m multiplet br broad data were reported in the following format chemical shift multiplicity coupling constant s j in hertz hz integrated intensity all the reagents solvents catalysts for which the synthesis is not described are purchased from chemical vendors such as sigma aldrich fluka bio blocks combi blocks tci vwr lancaster oakwood trans world chemical alfa fisher maybridge frontier matrix ukrorgsynth toronto ryan scientific silicycle anaspec syn chem chem impex mic scientific ltd however some known intermediates were prepared according to published procedures usually the.