Since we expected the nucleophilicity of the pyridine amine to be low, we decided to prepare the backbone building block as a dipeptide. By doing so, we could employ the same synthesis strategy as the Fairlie group used for Sanguinamide A. The synthesis of the dipeptide fragment for series B started from 6-aminopyridine-2-carboxylic acid which was first converted to methyl ester 1 using thionyl chloride in methanol (Scheme 1). We next attempted to directly couple the aminopyridine 1 to Boc protected leucine, but the poor nucleophilicity of the amine did not yield the desired product under a variety of conditions as speculated. Since stronger carboxylic acid activation conditions are not desirable, as they could lead to racemization at the leucine α-carbon, we instead attempted to improve the nucleophilicity of the amine. This was efficiently achieved by converting the pyridine to N-oxide 2 using m-CPBA. The amide bond formation now proceeded smoothly, and subsequent saponification directly yielded the dipeptide fragment 6 for peptide SA-B2. Reduction of 3 in the presence of B 2 pin 2 , followed by saponification yielded fragment 5 for peptide SA-B1. The fragments for the SA-C series were synthesized starting from 2,6-pyridinedicarboxylic acid (Scheme 2). Both carboxylic acids were esterified using thionyl chloride in methanol followed by a short reduction to selectively convert one of the esters to alcohol 8. The alcohol was then converted to chloride 9 using thionyl chloride followed by quantitative azidation (10) and hydrogenation over palladium on carbon to provide the amine 11 in very good yields. The amine was then coupled to Boc-L-Ile-OH and either directly saponified to yield dipeptide 13 (for peptide SA-C1) or oxidized using m-CPBA followed by saponification to yield fragment 15 (for peptide SA-C2). The synthesis of the fragments for the SA-D peptides started from 2-amino-6-methylpyridine by first Boc-protecting the amine (Scheme 3). Next, the methyl group was carboxylated using diethylcarbonate and LDA to form compound 17. After oxidation of the pyridine nitrogen using m-CPBA (18), the Boc group was removed using TFA to yield the free amine which could then be coupled to Boc-L-Ile-OH. Compound 20 was then either directly saponified or reduced before saponification to yield compounds 22 and 23 respectively.