Fmoc-Ala

The first set of three amino acids are Fmoc-Ala-OH, Fmoc-Phg-OH, and Fmoc-Feu-OH, all purchased from Novabio-chem. 

In the same manner the BAL handle derivatives of Fmoc-Gly-OMe, Fmoc-glycinal dimethylacetal, Fmoc-Ala-OtBu, Fmoc-Leu-OtBu, Fmoc-Phe-OMe, and Fmoc-Phe-OtBu were prepared. 

Fig. 6. 500 MHz H HRMAS NMR spectra of FMOC-Ala-Ile-Asp-Wang swollen with DMF- 7 and spun at 5 kHz. Spectra were obtained without (a) and with (b) using a ID TOCSY variant54 to reduce polymer signals. Note the substantially reduced signals arising from polystyrene in the aromatic (6.5-7.5 ppm) and aliphatic (1.5-2.5 ppm) regions.

Cll Cl/rFA Httnig Base 4 eq Fmoc-Ala-Oft DIC.HOBt. DMF Ac20 DMF/Mofpholine 1 1 3eq Fmoc-Pro-OH, DIC. HOBl. DMF Ac20/Pyridinc... 

Peptide 55 was synthesized using a segmental approach where the phosphine sulfide amino acid 50 was coupled as a dipeptide with Ala 56, and the Aib as either a dipeptide Fmoc-Ala-Aib or a tripeptide Ac-Ala-Aib-Ala. Wang, RapidAmide, or Rink resins can be used depending on the C-terminal group desired. 

A well-stirred soln of V-Teoc-(aTfm)Xaa-OMe (2 mmol), Fmoc-Xaa-F (3 mmol) and tetra-ethylammonium fluoride (cat. amount) in MeCN (3mL) was heated at 50 °C under an inert gas atmosphere until complete conversion was reached (usually 1-2 weeks, as monitored by 19F NMR spectroscopy). The solvent was removed and the product purified by flash chromatography Fmoc-Gly-(aTfm)Leu-OMe, yield 77% Fmoc-Ala-(aTfm)Leu-OMe, yield 77% Fmoc-Ala-(aTfm)Phe-OMe, yield 55%. 

The peptide was prepared by standard Fmoc/tBu procedures on Fmoc-Ala-trialkoxybenzhydryl-resin with Fmoc-Lys(Boc)-OH, and purified by preparative HPLC. After the Boc group was removed as described for the c[-Gly-Lys-]6, the hexahydrotrifluoroacetate salt of the 18-mer (550 mg) was dissolved in DMA (15 mL), followed by the addition of a soln of Msc-OSu (392 mg, 7 equiv) in DMA (1 mL) and DIPEA (436 mL, 12 equiv). After 90 min at rt, additional Msc-OSu (5.4 equiv) was added. After 5 h, the mixture was concentrated in vacuo to -5 mL, it was poured into ice-cold H20 (50 mL) and then 1M HC1 (40 mL) was added. The oily precipitate was collected by centrifugation, washed with Et20 (3 x 40 mL), and then redissolved in TFE/DMSO (1 1, 70 mL). TFE was removed and the remaining soln lyophilized from DMSO. This procedure was repeated once yield 530 mg (89%). 

The pentapeptide sequences were assembled on a Fmoc-Val-Pepsyn-KA-resin (0.08 mequiv-g 1) using a Biolynx synthesizer. Fmoc(Fmoc-Hmb)N-Gly-OH was incorporated using its pentafluorophenyl ester with HOBt catalysis for 45 min. Fmoc-Ala-OPfp was double coupled to the terminal (Hmb)tripeptide-resin for 2 h. All couplings not involving an Hmb-substituted residue were performed using standard 0.5 mmol scale coupling protocols. 

Fmoc-Ala-Oxa(5-Me)-OH was synthesized according to the same procedure described above for Fmoc-Ala-Oxa-OH. The acylation reaction was performed with commercially available Fmoc-Ala-NCA. yield 50% mp 103-108 °C TLC (CHCI s/MeOH/AcOH 85 15 5) R, 0.32. 

Scheme 4.1 Synthesis of oligopeptide conjugates. Reaction conditions and reagents (a) n-BuLi, THF, -78°C->0°C 1(3-bromopropyl)-2,2,5,5-tetramethyl-l,l-aza-2,5-disilacyclopentane THF/HCl (b) Fl2 (lOObar), Pd/C, toluene, 80°C, 3 days (c) Fmoc-Ala-OH, EDCI/HOBt, TEA, DCM, -40°C r.t. (d) piperidine, chloroform (e) Fmoc-Ala-Ala-OH, PyBOP, DIEA, DCM, r.t.

Fmoc-amino acid derivatives Fmoc-Ala-OH, Fmoc-Asn(Trt)-OH, Fmoc-Asp(0 Bu)-OH, Fmoc-Cys(Acm)-OH, Fmoc-Cys(Trt)-OH, Fmoc-Gly-OH, Fmoc-Pro-OH, Fmoc-Tyr( Bu)-OH, and Fmoc-Val-OH (Novabiochem). 

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