SYNTHESIS OF NANOTUBULE-FORMING CYCLIC OCTAPEPTIDES VIA AN FMOC STRATEGY

New syndiotactic cyclic octapeptides, namely cycle -D-Phe-L-Asp-D-Phe- L-Asn-D-Phe-L-Asp-D-Phe-L-Asn-) (1) and -D-N-MeAla-L-Asn-D-N-MeAla-L-A sp-D-N-MeAla-L-Asn-) (2), have been prepared, and preliminary structur al studies have been conducted. The synthesis of the linear peptides w as performed by using Fmoc chemistry, and head-to-tail cyclization was accomplished by using an orthogonal protection strategy and a support -bound cyclization step. Acidification of aqueous solutions of cyclic octapeptide (1) initiated formation of needlelike crystals whose morph ology and infrared absorption behaviour suggested that they were hydro gen-bonded nanotubular aggregates Of (1).