Recrreil. JoiwnuI qf tlte Rojml Netherlands Chemical Sociely. 102/12, decemher 1983 537 triester) (Fig. 3). I3C{'HJ. NMR (CDCI,): F 20.6 (s, CH, acetyl); 98.8, 30.7, 25.3, 19.5, 63.0 (s,; 36.1 (d, 35,-, 13 Hz, CBr,); 79.4 (broad, C-H,CBr,); 62.9 (broad), 67.0 (broad), 73.8 (d), 77.8 (broad) (m, glycerols); 55.2 (s, OCH, MMTR); 86.6 (s, C-tert MMTR); 101. 2-100.8, 70.9-71.2, 72.7, 68.3, 71.8, 61.7 (s, 3 x CI'-C6' glucose); 146.3 (d), 125.3 (dd), 130.4, 126.1 (d), 128.1, 121.6 (m, 113.2, 127.0, 128.3, 130.5, 134.9, 143.9, 158.6 Deblocking ./the 2.2.2-tribromoethyl-protecting group of the fully protected teiclioic uci~1,frugment 8a to ufford 8b Activated zinc was added to a solution of compound 8a (320 mg, 0.153 mmole) and 2,4,6-triisopropylbenzenesulfonic acid (5 mg) in pyridine (0.8 ml). After the addition of 2,4-pendanedione, the temperature of the reaction mixture rose and, after 5 min, the mixture was filtered to remove excess zinc. TLC analysis (chloroform/methanol, 97.5/2.5, v/v) showed almost complete conversion of the starting compound 8a ( R , 0.44) into base-line material. The filtrate was diluted with chloroform (50 ml) and washed with aqueous triethylammonium bicarbonate (2 x 50 ml, IM, pH 8.5). The organic layer was evaporated to an oil and the crude material applied to a column of Kieselgel 60 (10 g) suspended in chloroform/methanol (95/5, v/v) Removul ofthe 2-chlorophenyl und acetyl protecting groups from 8b to give conipouncl8dThe 2-chlorophenyl-protecting group was selectively deblocked from 8b without affecting the acetyl functions by treating compound 8b (I90 mg, 0. I mmole) with .syn-4-nitrobenzaldoximc (I65 mg, 1 mmole) and N1,N1,N3,,N3-tetramethylguanidinc (104 mg, 0.9 mmole) in dry T H F (2.5 ml). After 16 h at 2OOC. reversed-phase TLC analysis (RP-18) (0.05M aqueous TEAB/ acetone, 2/3, v/v) revealed complete conversion of starting compound 8b ( 4 0.55) into the 2-chlorophenyl-deblocked derivative 8c ( R , 0.86). Aqueous ammonia (10 ml, 25%) and T H F (5 ml) were added and the mixture was left for 16 h at 2OOC. The dark orange solution was concentrated under reduced pressure and the residue was redissolved in 80% aqueous methanol (4 ml). The crude mixture was then neutralized with acetic acid. After removal of the precipitate by filtration, the crude product was applied to a column (25 cm x 6 cm') of DEAE-Sephadex A25 ( H C 0 , -form) suspended in 0.05M TEAB/methanol ( l / l , v/v). Elution of the column was effected using a gradient (see Fig. 4,I) of O.OSM TEAB, 50% methanol -+ 0.5M TEAB, 75% methanol, the flow being 30 ml per h. Fractions of 6 ml were taken and those of the main peak were analyzed by reversed phase HPLC (RP-8).Fractions containing only 8d were evaporated down to a small volume, coevaporated three times with 25 % aqueous ammonia (40 ml) and lyophilized. The coevaporation was repeated (3 x 40 ml 25% aqueous ammonia) and the dissolved product was again lyophilized to give pure compound W as a fluffy material.Yield 107 mg (NH,') (87%). Final deblocking of the MMTR an...
