ABSTRACT
The first highly enantioselective Baeyer-Villiger oxidation of quaternary carbon-containing cyclobutane-1,3-diones using chiral phosphoric acid catalysis and commercially available oxidants was reported. According to the structure of the substrates, two optimized reaction conditions were developed to afford the corresponding chiral tetronic acid products in ≤93% and ≤95% ee values. This reaction offers the first catalytic asymmetric approach to chiral 5,5-disubstituted tetronic acid derivatives. The synthetic potential of this method has been demonstrated by the formal asymmetric synthesis of (-)-vertinolide and the first catalytic asymmetric total synthesis of plakinidone B.
ABSTRACT
A chiral phosphoric acid-catalyzed enantioselective condensation of 2,2-disubstituted cyclobutane-1,3-diones with a primary amine is described. This reaction offered a mild and efficient protocol for constructing quaternary carbon-containing cyclobutanes in good to high yields and enantioselectivities. This reaction is the first catalytic desymmetrizing carbonyl-amine condensation reaction and also represents the first catalytic desymmetrizing reaction of prochiral cyclobutane-1,3-dione.
ABSTRACT
<p><b>BACKGROUND</b>The purpose of this study was to investigate the feasibility of avoiding axillary lymph node dissection (ALND) for patients with only one sentinel lymph node (SLN) metastasis. The characteristics and predictive factors for non-sentinel lymph node (NSLN) metastasis of patients with single positive SLN were also analyzed.</p><p><b>METHODS</b>Patients with no and only one SLN metastasis (0/n and 1/n group, n ≥ 2) were selected from 1228 cases of invasive breast carcinoma, who underwent axillary dissection in Shandong Cancer Hospital between November 1999 and December 2011, to compare the characteristics of NSLN metastasis between them. For the 1/n group, the factors that influenced the NSLN metastasis were analyzed by univariate and multivariate analysis.</p><p><b>RESULTS</b>Differences of the NSLN metastasis between the 0/n and the 1/n groups were significant (P < 0.001). There was no significant difference between the axillary lymph node metastasis on level III in 1/n group and 0/n group (P = 0.570). When the total SLN number was ≥ 4 and with one positive case, the NSLN metastasis was not significantly different from that in the 0/n group (P = 0.118). In the 1/n group, clinical tumor size (P = 0.012), over-expression of Her-2 (P = 0.003), tumor grade (P = 0.018) and the total number of SLN (P = 0.047) significantly correlated with non-SLN metastasis. Clinical tumor size (P = 0.015) and the expression of Her-2 (P = 0.01) were independent predictive factors for non-SLN metastasis by the Logistic regression model.</p><p><b>CONCLUSION</b>Under certain conditions, breast cancer patients with single SLN metastasis could avoid ALND.</p>
