[Cs].[Cl-].C([NH:10][C@H:11]([C:17]([OH:19])=[O:18])[CH2:12][CH2:13][CH2:14][CH2:15][NH2:16])(OC(C)(C)C)=O.C(=O)([O-])[O-].[Cs+].[Cs+]>CO.O>[NH2:10][C@H:11]([C:17]([OH:19])=[O:18])[CH2:12][CH2:13][CH2:14][CH2:15][NH2:16]Attachment of N--Boc--Lys(Cl--z) to chloromethyl resin was performed by the cesium salt method. A sample of chloromethyl resin (200 g.) containing 0.74 mmol chloride per gram is treated with the cesium salt of Boc--Lys--(Cl--z) resulting from the neutralization of Boc--Lysine with cesium carbonate. About 73.8 grams of Boc--Lysine is dissolved in 80% methanol and 20% water and adjusted to pH 7.0 with about 29 grams of cesium carbonate. The resulting solution is dried on a rotary evaporator, then dried three more times after three additions of 100 milliliters of xylene. To the cesium salt of Boc--Lys(Cl--z) was added 200 grams of chloromethyl resin as above and sufficient 1-Methyl-2-Pyrrolidinone to make about 1.90 liters total volume. The resulting mixture is stirred at 55° C. for 48 hours. The resin was then washed extensively with methanol, then water, then again with methanol. The resin was air dried, then dried under vacuum. After cleavage of lysine from the resin with HF, amino acid analysis gave one peak corresponding to 0.36 mmol/gm.
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