those skilled in the art of organic synthesis protection and deprotection of functional groups in the processes below may be carried out by procedures generally known in the art see for example t w greene amp p g m wuts u201c protecting groups in organic synthesis u201d 3 rd edition wiley 1999 which is hereby incorporated by reference examples of u201c protecting group u201d of oxygen or nitrogen include but are not limited to acyl e g acetyl formyl benzoyl etc carbonate e g roc o u2014 where r can be substituted or unsubstituted alkyl alkenyl aryl benzyl or the like carbamate e g r a r b n u2014 c o u2014 wherein r a and r b are each independently hydrogen alkyl aryl or the like the oxygen and nitrogen protecting groups may also include unsubstituted or substituted benzyl groups allyl t butyl groups or silyl groups which can be removed readily by methods well known in the art in particular suitable nitrogen protecting group is exemplified by benzyl bn tert butoxycarbonyl boc tert butyldimethylsilyl tbdms or the like the term u201c leaving group u201d as used herein refers to a group that can be replaced by another through a reaction such as displacement suitable leaving groups include but are not limited to halogen cl br i and sulfonates u2014 os o 2 aryl e g u2014 os o 2 ph or u2014 os o 2 c 6 h 4 ch 3 p or u2014 os o 2 alkyl e g u2014 os o 2 ch 3 or u2014 os o 2 cf 3 or the like u201c pharmaceutically acceptable salt u201d includes.