or can be prepared by known methods or by specific reaction schemes described herein the compounds of the present invention may be readily prepared by standard solid phase or solution phase peptide synthesis procedures using starting materials and or readily available intermediates from chemical supply companies such as aldrich or sigma h paulsen g merz v weichart 34 solid phase synthesis of o glycopeptide sequences 34 angew chem int ed engl 27 1988 h mergler r tanner j gosteli and p grogg 34 peptide synthesis by a combination of solid phase and solution methods i a new very acid labile anchor group for the solid phase synthesis of fully protected fragments tetrahedron letters 29 4005 1988 merrifield r b 34 solid phase peptide synthesis after 25 years the design and synthesis of antagonists of glucagon 34 makromol chem macromol symp 19 31 1988 a preferred method of preparing compounds of the present invention is by the solution phase method depicted in scheme i below str5 wherein a b e f g r m n p and r are as defined hereinabove a 39 e 39 f 39 g 39 and r 39 are a b e f g and r respectively or are protected analogues thereof or precursor substituents thereto and p 1 p 2 and p 3 are amino acid protecting groups the compounds of the present invention are available generally by initially coupling the appropriate amino acid or other appropriate z group precursor where z is as defined hereinabove which contains a free primary or secondary amine to the free carboxylic acid portion of a protected derivative of aspartic acid the functional groups of aspartic acid or any functional groups.