Zq. You et al., SUPPRESSION OF THE MATTOX REARRANGEMENT OF 16-ALPHA-CYANOPREDNISOLONES IN ACID - SYNTHESIS OF METHYL 16-ALPHA-PREDNISOLONECARBOXYLATES, Tetrahedron letters, 36(19), 1995, pp. 3303-3306
Prednisolone derivatives with a 16 alpha-methyl carboxylate group were
synthesized by a novel procedure of 1,3-dipole addition of fulminic a
cid to 21-acetyloxy-11 beta-hydroxy-3,20-dioxo-1,4,16-pregnatriene, fo
llowed by base-catalyzed ring opening of the resulting isoxazoline to
yield a 16 alpha-cyanoprednisolone derivative and treatment of the nit
rile with methanolic HCl. Conversion of the cyanosteroids in the acid
to the corresponding methyl carboxylates was achieved with or without
the Matron rearrangement by controlling reaction temperature and prote
ctive group for the 21-OH.