The chromium VI oxidative cleavage of bridgehead alcohols

A simple asymmetric synthesis of 4-arylphenylalanines via palladium-catalyzed cross coupling reaction of arylboronic acids with tyrosine triflate

“…The organic phase was dried over MgS04 and concentrated to an oil. The oil was purified by column chromatography (silica gel, hexane/ethyl acetate (2/1)) to give 7.75 g (91%) of colorless 1 which crystallized on standing: mp 47-48 °C; [a]20D +33.6°(c = 1, CHC13); NMR (CDC13) 6 7.2 (s, 4 H, ArH), 5.05 (d, J = 7.1 Hz, 1 H, NH), 4.6 (m, 1 H, a-CH), 3.7 (s, 3 H, OCH3), 3.17 (m, 1 H, CHH), 3.03 (m, 1 H, CHH), 1.4 (s, 9 H, C(CH3)3). Anal.…”

“…(d, J = 8. 3 Hz, 1 , NH), 4.65 (m, 1 H, a-CH), 3.75 (s, 3 H, OCH3), 3.02 (m, 2 H, CH2), 1.4 (s, 9 H, C(CH3),); CIMS m/z (relative intensity) 356 (M+ + 1) (18), 300 (M+ + 1 -C(CH3)3) (69), 256 (M+ + 1 -C02C(CH3)3) (100). Anal.…”

“…(S)-Methyl a-amino-4'-methyl(l,l'-biphenyl)-4-propanoate hydrochloride salt (4b): mp 207 °C dec; [a]20D +11.83°( c = I, CH3OH); NMR (CDC13) 8.72 (s, 3 H, NH3), 7.67 (dd, J = 7.6, 7.8 Hz, 4 H, ArH), 7.28 (dd, J = 7.9, 7.8 Hz, 4 H, ArH), 4.28 (t, J = 6.2 Hz, 1 H, a-CH), 3.67 (s, 3 H, OCH3), 3.17 NMR (CDC13) 6 8.73 (s, 3 H, NH3), 7.67 (dd, J = 8.6, 8.2 Hz, 4 H, ArH), 7.52 (d, J = 8. 3 Hz, 2 H, ArH), 7.35 3 H, OCH3), 3.2 (m, 2 H, CH2); CIMS m/z (relative intensity) 290 (M+ + 1 -HC1) (100 (S )-4-( 1-Naphthalenyl)phenylalanine methyl ester hydrochloride salt (4d): mp 176-177 °C; [a]20D +9.41® (c = 1, CHgOH); NMR (CDC13) 8.77 (s, 3 , NH3), 8.0 (dd, J = 8.1, 8.2 Hz, 2 H, NapH), 7.8 (d, J = 8.0 Hz, 1 H, NapH), 7.35-7.6 (m, 8 H, ArH + NapH), 4.35 (t, J = 6.2 Hz, 1 H, a-CH), 3.72 (s, 3 H, OCH3), 3.26 (m, 2 H, CH2); CIMS m/z (relative intensity) 306 (M+ + 1 -HC1) (100). Anal.…”

Metal-Mediated Oxidation of Tertiary Alcohols and Related Fragmentations

“…Reaction pathway for oxidation of tertiary cyclopropanols with chromic acid Although their conversion is low, Cawley and Spaziano showed that norbornanol derivatives are able to undergo oxidation in a same way. [35] The CϪC bond cleavage occurs on C 1 ϪC 2 or C 1 ϪC 7 bonds, depending on the nature of the substituents. Two kinds of product are thus obtained (Scheme 26).…”

Oxidative Transformations of Guaia-1(10)-en-12,8-olides into Xanthanolides

“…Cleavage products are commonly found in chromic acid oxidation. − For instance, it has been demonstrated that oxidation of a tricyclic diterpenoid with Jones's reagent affords a ring B-opened, substituted p -benzoquinone . A possible route leading to the formation of 3 and 4 is shown in Scheme .…”