Mefp1 is a protein produced by the marine mussel, Mytilus edulis, which helps the organism to adhere to surfaces in turbulent waters. To better understand the nature of the adhesion process, we sought to synthesize homogeneous oligopeptides based on the repeating decapeptide unit of the protein. The fully protected decapeptide 10 has been synthesized from appropriately protected amino acid building blocks using a fragment condensation strategy. A key feature of the strategy is the late incorporation of the synthetically valuable dihydroxyproline residue. This synthesis of the orthogonally protected repeating decapeptide unit of Mefp1 represents an important first step toward producing useful quantities of homogeneous oligopeptides related to the protein.

L-2,3-trans-3,4-cis-N-Fluorenylmethoxycarbonyl-3,4-dihydroxy-3,4-O-isopropylidineproline (9) has been prepared from D-gulonolactone in nine steps and an overall yield of 22%. Compound 9 has been converted to its allyl ester 13. Compounds 9 and 13 were investigated as building blocks for the incorporation of dihydroxyproline into peptides, with compound 9 serving as a carboxyl component and compound 13 as a precursor to an amino component for peptide coupling reactions. Their utility was demonstrated by the synthesis of dipeptides 11 and 15.

A general strategy is proposed, wherein a pentose sugar gamma-lactone can be converted, via a series of nine reactions, to a 3,4-dihydroxyproline, suitably protected for use in peptide synthesis. Thus, D-ribonolactone (6) has been converted to N-fluorenylmethoxycarbonyl-3,4-di-O-tert-butyldimethylsilyloxy-D-2,3-cis-3,4-cis-proline (7) in 18.9% overall yield. Likewise, L-arabinonolactone (11) has been converted to N-fluorenylmethoxycarbonyl-3,4-di-O-tert-butyldimethylsilyloxy-L-2,3-cis-3,4-trans-proline (36) in 13.7% overall yield and L-lyxonolactone (12) to N-fluorenylmethoxycarbonyl-3,4-di-O-tert-butyldimethylsilyloxy-L-2,3-trans-3,4-cis-proline (37) in 11.2% overall yield. These building blocks have also been fully deprotected to give the free amino acids. We believe that this series of reactions ought to be applicable to the synthesis of any of the eight stereoisomers of 3,4-dihydroxyproline, by judicious selection of the pentose starting material.

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