Direct preparation of bromoacetaldehyde

Abstract

Halo aldehydes or their equivalents have been widely employed in heterocyclic synthesis. Such aldehydes are useful for ring-forming reactions in that they represent units with two adjacent electrophilic sites. However, the simplest representatives, bromo-or chloroacetaldehyde, have been little used because the anhydrous aldehyde is difficult to prepare. J. Org. Chem. 1983,48, 2111-2112 2111 the solid residue, dissolved in MeOH, was filtered and dried in vacuo, followed by HPLC separation (Altex columns with MeOH/H20 (91) as mobile phase), to yield 1.5 mg of 2b and 32 mg of starting compound lb. The high-resolution mass and 'H NMR spectra of 2b were identical in all respects with those of natural 2b. Disciplines3@,11-Dihydroxy-9,11-secogorgost-5-en-9-one (la):' absorption spectrum tm 51; CD -3350, -4800.Isomerization of 3/3,1l-Dihydroxy-9,ll-secogorgost-5-en-9-one (la) to 8a-H Isomer 2 a A 50-mg eample of la was treated in the same way as described above for lb. The final HPlC separation yielded 2 mg of 2a (HPLC rrt 0.14 with cholesterol = 1) and 35 mg of la. Absorption spectrum of 2a: c2a 147; CD Acetylation of l b and 3b to 3@,11-Diacetoxy-24-methylene-9,ll-secocholest-5-en-9-one (4b). Both lb and 3b were acetylated under standard conditions (AczO/py, room temperature, 2 h) to yield the same diacetate 4b, which was purified by HPLC on Altex columns with MeOH/H20 (

Antineoplastic agents. 93. Structure of the Bugula neritina (marine bryozoa) antineoplastic component bryostatin 3

“…Indeed, present evidence suggests that substantial structural modifications can be made in the bryostatin ester substituents while preserving antineoplastic activity. In addition to the obvious potential of the bryostatins for eventually contributing to improvements in cancer treatment as the original biosynthetic product or through structural modifications, (6) So far bryostatin 1 has been shown in studies conducted by the NCI to display very potent (low dose) activity against, e.g., the murine PS (52-96% life extension at 10-70 Mg/kg), L1210 (lymphocytic leukemia, 34-51% life extension at 37.5-150 Mg/kg), and M5 (M5076 ovarian carcinoma, 40-48% life extension at [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] Mg/kg and 20-65% curative in the tumor regression model at 20-40 Mg/kg) key experimental tumor systems.…”

Toward a Practical Synthesis of Morphine. The First Several Generations of a Radical Cyclization Approach

“…The "open" form, 91, can be synthesized easily by a conversion of halide or azide of the side chain to a carbamate and its condensation with α-bromoacetaldehyde (or its dimethylketal), obtained by the method of Kraus by ozonolysis of 1,4-dibromobut-2-ene. 36 The closure of the radical such as 90 may lead to maximization of the correct C14/C9 absolute stereochemistry through the less convex shape.…”

Biomolecular Assemblies: Moving from Observation to Predictive Design

“…As mentioned above, all-atom MD is far too computationally expensive to cover the time and length scales of a protein folding reaction for a larger protein. Thus, in this study the authors leveraged a course-grained model 350 that reduced each sidechain to a unified bead. Hence, MLAc was modelled as beads on a string with information regarding the final topology remaining intact.…”

“…As mentioned above, all-atom MD is far too computationally expensive to cover the time and length scales of a protein folding reaction for a larger protein. Thus, in this study the authors leveraged a course-grained model that reduced each side chain to a unified bead. Hence, MLAc was modeled as beads on a string with information regarding the final topology remaining intact. , In this landmark study, theoretical predictions of both the detailed folding mechanism and global and local structural changes were found to be nearly identical to experimental results (Figure ).…”