added dropwise, at 0' and under nitrogen, a solution of IV in methylene chloride (5 ml). The addition took 10 min. The reaction was allowed to reach room temperature and then refluxed for 24 hr. At that time, a 30% excess of isopropylidene-sn-glycerol was added and the reaction was refluxed for an additional 16 hr or until TLC indicated maximum conversion.
The reaction mixture was diluted with ether and washed successively with 3 N hydrochloric acid, 5% sodium bicarbonate, and water. The bicarbonate extract was acidified with concentrated hydrochloric acid to give 1.92 mCi of l-lPC-adamantanecarbylic acid. The organic layer was dried over magnesium sulfate, filtered, and concentrated to dryness under aspirator vacuum. The residual oil was used directly in the next step. The radiochromatographic purity of the product was 95% as determined by TLC.
In a typical cold run, the reaction was stopped after 24 hr of refluxing in methylene chloride. After workup in the usual manner, the residual clear oil was stored in a stoppered glass vial at 4' . After a few days, a white solid crystallized out of the oil. The solid was triturated with cold acetonitrile and vacuum filtered to give 0.060 g, mp 204-205'; IR (KBr): 1810 and 1730 cm-l; NMR (CDCb): 1.9 (m, 18H) and 1.7 (m, 12H) ppm; mass spectrum mle 168, 135; identical to an authentic sample of adamantanecarboxylic anhydride prepared by the method of Stetter and Rauscher (7).
3-(a-'4C-l-AdamantoyI)-sn-glycerol (VI1)-A solution of V in ether (2.5 ml), methanol (1 ml), and 3 N hydrochloric acid (0.4 ml) was stirred magnetically at room temperature for 16 hr. An additional 0.2 ml of 3 N hydrochloric acid was added, and the mixture was stirred for 15 hr or until TLC indicated complete conversion. The reaction mixture was diluted with ether and washed successively with water, 5% sodium bicarbonate, and saturated sodium chloride solution. The organic layer was dried over sodium sulfate, filtered, and concentrated to dryness under aspirator vacuum. The residual oil was used directly in the next step. The radiochromatographic purity of the product was 98.5% as determined by TLC. l,2-Dioleoyl-3-(a-'4C-l-adamantoyl)-sn-glycerol (1)-To a solution of VII in methylene chloride (2 ml) was added pyridine (0.48 g, 6 mmoles) in methylene chloride (1 ml). The solution was cooled to 0-5' in an ice-water bath. To this magnetically stirred solution under nitrogen atmosphere was added dropwise oleoyl chloride (1.8 g, 6 mmoles) in methylene chloride (3 ml) over 5 min. The reaction was allowed to reach room temperature, stirred magnetically for 15 hr, diluted with ether, and washed successively with water, 3 N hy-drochloric acid, 5% sodium bicarbonate, and saturated sodium chloride solution.
The ether solution was dried over sodium sulfate, filtered, and concentrated under aspirator vacuum to an oil. The oil was dissolved in 2 ml of petroleum ether-ether (1:l v/v) and applied to a glass column packed with 50 g of magnesium silicate. The column was eluted with five 30-ml volumes of petroleum ether-ether (1:1 v/v). Fractions 4 and 5, which contained the desired product, were combined and evaporated to an oil under a vacuum of 5 pm. The residual oil weighed 1.35 g (13.8 mCi). The radiochemical yield was 63.8% (based on HI), and the radiochromatographic purity was 94.3% as determined by TLC (Fig. ); the specific activity was 8 mCi1mmole.