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The development of a new strip biopsy technique for endoscopic mucosectomy utilizing endoscopic saline injection and a double-channel endoscope permits the safe and simple resection of superficial type early gastric cancer which has been difficult to perform with conventional polypectomy techniques. Preresection assessment of the depth of invasion and postresection assessment of efficacy are important with regard to treatment of early gastric cancer, but conventional endoscopic ultrasonography employed for this purpose requires special equipment and involves intricate procedures. An ultrasonic probe which can be used endoscopically has recently been developed and is currently in the trial stage. The authors have conducted studies with respect to a 7.5 MHz radial scanning type Miniature Ultrasonic Probe as well as a 20 MHz manual linear scanning type Sonoprobe System. Experimental studies indicated that the former type is capable of delineating postresection ulcers, while the latter permitted delineation of tumors as hypoechoic images in 9 of 11 cases of early gastric cancer.

150was added. The aqueous layer was extracted with CH2CI, (3 X 5 mL), and combined CH2C12 layers were washed with 5% aqueous NaHCO, ( I x 10 mL) and H 2 0 (1 X 10 mL), then dried, filtered, and concentrated. Chromatography (9.9:O.l CHCI,/MeOH) afforded 24 (0.019 g, 68%): mp 169-171 OC (EtOAc/ether); IR (CHCI,) ,958,914 cm-I; 'H NMR (60 (s, 6 H), 1.37 (s, 3 H); MS calcd for C14H,,03 (M+-S02Me) 233.1178, found 233.1 155. Procedure for the Conversion of Mercapto Adducts 15 and 20 into Methylthio Adducts 16 and 21, Respectively. Diazabicyclo[5.4.0]undecene (DBU) (1 9 pL, 0.123 mmol) and CH31 (0.1 mL, 1.6 mmol) were added to a solution of the mercapto adduct (0.021 g, 0.0616 mmol) in anhydrous benzene (IO mL). The reaction mixture was stirred for 2 days, then washed with 1 N HCI (3 X IO mL) and H 2 0 ( I X IO mL), dried, filtered, and concentrated to give the corresponding thiomethyl adduct (0.022 g, quantitative yield).Conversion of Amino Adduct 29 into syn-N-Acetylamino Adduct 30. Acetic anhydride (0.5 mL) and pyridine (0.5 mL) were added to a solution of 29 (0.023 g, 0.071 mmol) in CH2C12 (7 mL). The solution was stirred for 23 h, then toluene was added, and the solution was concentrated to give 30 (0.026 g, quantitative yield).Preparation of 0-Acetyl Adduct 28. (Dimethy1amino)pyridine (DMAP) (0.025 g, 0.202 mmol) and acetic anhydride (0.2 mL, 2.0 mmol) were added to a solution of the hydroxy adduct 27 (0.046 g, 0.184 mmol) in anhydrous benzene (8 mL). The solution was refluxed for 3.5 days. Additional 4-(dimethy1amino)pyridine (0.045 g) and acetic anhydride (0.2 mL) were added, and refluxing was continued for 2 more days. TLC showed that the reaction was still incomplete; however, the solution wsa allowed to cool, diluted to 5 mL with EtOAc, washed with 5% (v/v) HCI ( 1 X IO mL) and brine (1 X IO mL), dried, filtered, and concentrated. Chromatography (8:2 petroleum ether/EtOAc) yielded 28 (0.030 g, 52%): mp 136-138 OC (ether); IR (CHCI,)

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