Regioselectivity epoxide ring opening

Displacement of the 3-hydroxyl group of 74 was carried out with Et2NSF3 (DAST) (DAST - diethylaminosulfur trifluoride) in dichloromethane. The expected fluorinated product 75 on treatment with aqueous perchloric acid led to regioselective epoxide ring opening to give 76, which on treatment with hydrazine hydrate at 100 °C for 18 h yielded 3,4-dihydroxy-8-oxo-octahydropyridazino[l,6-r/][l,2,4]triazine-l-carboxylic acid phenylamide 77 (Scheme 3) <1997T9357>. 

Two classes of structures containing azido- and aziridino-hydroxyl-(3-lactam (I and II, respectively, Fig. 21) have been prepared by means of a stereo- and regioselective epoxide ring opening reaction [296],... 

Very successful has been the aldolase-catalyzed aldol reaction as exemplified inO Scheme 14 [97]. The required (R)-3-thioglyceraldehyde (20) is obtained from regioselective epoxide ring opening of (5)-glycidaldehyde diethyl acetal with thioacetic acid and its potassium salt. Con-... 

The choice of the initiating acid allows the synthesis of constitutionally different cyclohexanes. A 6-endo reaction can also be initiated by regioselective epoxide ring opening with Lewis acids. Monocyclization involving ( )-olefins furnishes acetoxymethyl group are stereoselectively syr 18. 

Further monocyclizations can be initiated by regioselective epoxide ring opening. Ring closure occurs in a SN2-like process with inversion of configuration at the carbon atom involved in the new C-C bond31,32. 

D-Ribonolactone has also been used as starting material for a synthesis of 6-epi-trehazolin, 7, in which the key cyclopentanoid functionality and stereochemistry are introduced by diastereoselective epoxidation and regioselective epoxide ring opening by azide to convert 5 to 6 (Scheme... 

Fig. 8.42 Regioselective epoxide ring opening catalyzed by In(lll) salts with strong dependence on pH.

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