The identification of a novel series of benzamide-containing MCHr1 antagonists is described.

The major objective of the antifungal drug program at Abbott Laboratories was to develop a non-toxic drug, superior to amphotercin B, which could be used to treat the life threatening fungal infections. One such drug candidate (I) originated from the highly functionalized antifungal natural product echinocandins [1,2]. It showed high antifungal activity with the least toxicity. The key components of this candidate are a cyclic hexapeptide core and a lipophilic side chain (R). An efficient synthesis of this cyclic hexapeptide has been developed for the purpose of preparing multigram quantities of the product for SAR studies. The cyclic hexapeptide is composed of (2S, 4S)-4-amino-proline (Amp), two threonines, 4-hydroxyproline, homotyrosine (hTyr) and ornithine. The two segments selected for synthesis were Boc-Orn-Thr-Hyp-OH (II) and Fmoc-hTyr-Thr-AzP-OMe (III). Strategically, these segments were selected because they contain C-terminal proline derivatives, known to be less sensitive to racemization during segment condensation. In the synthetic scheme the 4-amino-proline was introduced as 4-azido-proline (Azp). Homotyrosine, now it is commercially available, was prepared by literature procedure [3,4] and converted to Fmoc-hTyr-OH by a standard procedure. Boc-Azp-OMe was prepared starting from Boc-Hyp-OMe. Boc-Hyp-OMe was converted to mesyl derivative by treatment with MS-Cl/pyridine. The mesyl derivative was then converted to Boc-Azp-OMe by treatment with sodium azide in DMF. Now this derivative is also available commercially. Segment II was prepared by a stepwise approach starting from Hyp-OBzl. HypOBzl was coupled with Z-Thr-OH utilizing the standard EDC/HOBt method to yield ZThr-Hyp-OBzl as a solid material. This dipeptide on hydrogenation and coupling with Boc-Orn(Fmoc)-OSu gave crude segment II. The crude peptide was purified by silica gel chromatography to give pure crystalline peptide II. The synthesis of segment III was also used the stepwise approach starting from Azp-OMe. The dipeptide Z-Thr-Azp-OMe was obtained as a crystalline solid by coupling Boc-Thr-OH with Azp-OMe with EDC/HOBt. The Boc group was removed from this dipeptide and the resulting product coupled with Fmoc-hTyr-OH using EDC/HOBt yielding segment III as a solid material. The removal of Fmoc from III followed by coupling with segment II using EEDQ produced the crude linear hexapeptide, which was then purified by silica gel chromatography. The linear