descriptive names and by reference to structures shown in appropriate charts and text in appropriate situations the proper stereochemistry an important aspect of this invention is also represented in the charts the compounds and processes of this invention may be divided into two groups the four groups are described in charts a and b within each group the reactions are shown as steps charts ag and bg are generic charts various substituted r groups are indicated the steps from charts ag and bg are generic steps that describe reactions that are specified to the degree needed to enable one ordinarily skilled in the art to practice the invention following the general procedures for each group are one or more detailed preparations and examples that describe precisely how to prepare specific compounds of this invention chart ax1 thus describes the experimental steps for one specific reaction sequence described in chart ag and bx1 shows a specific reaction from chart bg note that the generic charts as well as the specific reactions show the stereochemistry of the compounds the specific procedures are to be construed as merely illustrative and do not impose limitations upon the general reaction schemes in any manner whatsoever those skilled in the art will promptly.