Ure 22). It 36.75 (36.08), (36.08), 3-O-C(O)N(CH ) two.85, s 3-O-C(O)N(CH3)two 3 36.75 CH3 is

Ure 22). It 36.75 (36.08), (36.08), 3-O-C(O)N(CH ) two.85, s 3-O-C(O)N(CH3)two 3 36.75 CH3 is worth noting that the starting material silibinin (1) (bought from Fisher Scientific) 5-OMe 56.09, diastereoisomeric mixture of silybin A and silybin B. The car3.83, s s C-5C-5 5-OMe 56.09, CH 3.83, was a nearly equimolar CH3 3 7-OMe 55.70, CH three.78, s C-7C-7 7-OMe derivatives of CH3 3 55.70,five,7,20-O-trimethylsilybin are s three.78, as a result diastereoisomeric mixtures as bamoyled three.87, s s C-19 19-OMe 56.01, CH3 19-OMe 56.01, CH C-19 properly, and some NMR signals3 of these derivatives3.87, pair 3.89, hence seem as a C-20 (see Table 2 s 20-OMe 56.01, CH3 20-OMe 56.01, CH3 three.89, s C-20 and Materials and Procedures).2.three. Scope with the Reaction JPH203 Cancer ApproachThe selectivity may be caused by the hydrogen bonding between the hydrogen with the alpha-OH as well as the 4-carbonyl oxygen atom. To additional confirm that the secondary 3-OH in five,7,20-O-trimethylsilybin is often carbamoyled by using triethylamine and DMAP as bases, 5,7,20-O-trimethyl-23-O-TBS-silybin (10) was exposed for the identical set of reaction conditions, resulting in 3 3-O-carbamoyl-5,7,20-O-trimethyl-23-O-TBS-silybins (11, 12, and 13) in 457 yields with each other with all the Polmacoxib supplier recovered starting material ten (276 ), as shown in Scheme three. To further discover the applicability with the new carbamoylation strategy to flavanonols, the application of your very same set of reaction circumstances to three,4,five,7-O-tetramethyltaxifolin (14) led to C) in formation of 3 desired taxifolin derivaFigure 2. Crucial HMBC correlations (from H to the 5. Figure two. Important HMBC correlations (from H to C) in5. tives, 15, 16, and 17, in 381 yields as well as the recovered starting material 14 (322.3. (Scheme Reaction Strategy 45 )Scope of the4). This implies that the carbamoylation supplies a feasible method towards the selectivity may perhaps be flavonolignans but in addition 3-O-carbamoylated hydrogen of not only 3-O-carbamoylatedcaused by the hydrogen bonding amongst theflavanonols. the 1 Table 2. NMR data 4-carbonyl oxygen was C To further confirm open-chain -hydroxyl alpha-OH as well as the for 5ofH NMR: 300 MHz; 13also evaluated in thethat the secondary 3-OH The applicability ( the approach atom. NMR: 75 MHz). in five,7,20-O-trimethylsilybin can be carbamoyled by using triethylamine the DMAP as ketones. Acyclic 3-hydroxy-2-butanone (18) was (CDCl3) and treated with and respective Position 5 chosen bases, 5,7,20-O-trimethyl-23-O-TBS-silybin (10), was Hz) reaction C, (J in exposed to the very same DMPA HMBC (H (thio)carbamoyl chloride (4 eq) Sort presenceHof triethylamine (4 eq) andset ofC) (1 eq) in the situations, M). 80.96 1in 3 3-O-carbamoyl-5,7,20-O-trimethyl-23-O-TBS-silybins (11, two CH five.29 (five.27) d (11.eight) C-4, H-3 within the crude in DCM (0.1 resulting(80.89), The H NMR evaluation (Figure 3) on the characteristic C-13, C-14, C-3 74.67 (74.52), five.51 (five.49) d (11.eight) C-4, C-14, converted solution indicated that 54 and CH of 3-hydroxy-2-butanone (18) is often 3-OC(O)N- to 17 4 186.40, C the corresponding N,N-dimethylcarbamoyl item (19) and N,N-diethylcarbamoyl 4a 104.24, C item (20), respectively (Scheme 5). The all round conversion prices for the open-chain 5 164.18, C -hydroxyl ketones93.47, decrease than these for the cyclic -hydroxyl ketones, and no carare 6 CH 6.09.06, overlapped C-4a, C-7, C-Molecules 2021, 26,six of12, and 13) in 457 yields collectively with all the recovered starting material ten (276 ), as shown in Scheme 3. To further discover the applicability on the new carbamoylation process t.