Bryostatin 1 is a marine natural product that is a very promising lead compound due to the potent biological activity it displays against a variety of human disease states. We describe herein the first total synthesis of this agent. The synthetic route adopted is a highly convergent one in which preformed and heavily functionalized pyran rings A and C are united by "pyran annulation": the TMSOTf promoted reaction between a hydroxy allylsilane appended to the A ring fragment and an aldehyde contained in the C ring fragment, with concomitant formation of the B ring. Further elaborations of the resulting very highly functionalized intermediate include macrolactonization and selective cleavage of just one of five ester linkages present.Bryostatin 1 is a now well-known natural product originally isolated by Pettit and coworkers from the marine organism Bugula neritina. 1 Since that time, other members of this family have been isolated such that some 20 members are now known. 2 It has also been established that the true source of the bryostatins is not actually Bugula neritina, but rather a bacterial symbiont. 3 Interest in the bryostatins, and bryostatin 1 in particular, has been intense due to the wide range of potent bioactivity associated with bryostatin 1. Bryostatin 1 has shown activity against a range of cancers, and has also shown synergism with established oncolytic agents such as Taxol®. 4 This has led to the use of bryostatin 1 in numerous clinical trials for cancer, despite the absence of any renewable supply for this compound at present. In addition, bryostatin 1 has shown promising activity relevant to a number of other diseases and conditions, including diabetes, 5 stroke, 6 and Alzheimer's disease. 7 A clinical trial for Alzheimer's disease is commencing. 8 This wide range of promising potential indications for bryostatin 1 becomes more understandable when it is recognized that at least one mechanism for function of this agent involves activity on protein kinase C (PKC) isozymes and on other C1 domain containing proteins. 9 These signaling proteins are known to regulate some of the most critical cellular processes and properties, including proliferation, differentiation, motility and adhesion, inflammation, and apoptosis. 10 Given this backdrop, it is not surprising that synthetic activity directed towards the bryostatins has been intense. What is surprising, perhaps, is that bryostatin 1 itself has not been previously synthesized, while other members of the family have been prepared. Previous total syntheses include those of bryostatin 7 (2, by Masamune), bryostatin 2 (3, by Evans), bryostatin 3 (4, by Yamamura), and bryostatin 16 (5, by Trost). In addition, Hale has described a formal synthesis of bryostatin 7, and Trost has recently reported a synthesis of C20-epi-bryostatin 7. 11 * keck@chem.utah.edu .Supporting Information Available Experimental procedures and spectral data. This material is available free of charge via the Internet at http://pubs.acs.org. Another very important aspect...

From the enediyne class of antitumor antibiotics, uncialamycin is among the rarest and most potent, yet one of the structurally simpler, making it attractive for chemical synthesis and potential applications in biology and medicine. In this article we describe a streamlined and practical enantioselective total synthesis of uncialamycin that is amenable to the synthesis of novel analogues and renders the natural product readily available for biological and drug development studies. Starting from hydroxy- or methoxyisatin, the synthesis features a Noyori enantioselective reduction, a Yamaguchi acetylide-pyridinium coupling, a stereoselective acetylide-aldehyde cyclization, and a newly developed annulation reaction that allows efficient coupling of a cyanophthalide and a p-methoxy semiquinone aminal to forge the anthraquinone moiety of the molecule. Overall, the developed streamlined synthesis proceeds in 22 linear steps (14 chromatographic separations) and 11% overall yield. The developed synthetic strategies and technologies were applied to the synthesis of a series of designed uncialamycin analogues equipped with suitable functional groups for conjugation to antibodies and other delivery systems. Biological evaluation of a select number of these analogues led to the identification of compounds with low picomolar potencies against certain cancer cell lines. These compounds and others like them may serve as powerful payloads for the development of antibody drug conjugates (ADCs) intended for personalized targeted cancer therapy.

‘OH’ no you don't: The title compound 1 has been synthesized and evaluated for biological function. Molecular modeling of bryostatin 1 with the C1 domain of protein kinase C  δ indicates that the C9OH of bryostatin 1 makes a hydrogen‐bonding contact to the protein. Despite the absence of the hydrogen‐bonding contact for 1, it displays bryostatin‐like biological effects in four assays using either U937 leukemia cells or prostate LNCaP cells.

Herein, we report a systematic study of the Larock indole annulation designed to explore the scope and define the generality of its use in macrocyclization reactions, its use in directly accessing the chloropeptin I versus II DEF ring system as well as key unnatural isomers, its utility for both peptide-derived and more conventional carbon-chain based macrocycles, and its extension to intramolecular cyclizations with formation of common ring sizes. The studies define a powerful method complementary to the Stille or Suzuki cross-coupling reactions for the synthesis of cyclic or macrocyclic ring systems containing an embedded indole, tolerating numerous functional groups and incorporating various (up to 28-membered) ring sizes. As a result of the efforts to expand the usefulness and scope of the reaction, we also disclose a catalytic variant of the reaction along with a powerful Pd2(dba)3 derived catalyst system, and an examination of the factors impacting reactivity and catalysis.

A close structural analogue of bryostatin 1, which differs from bryostatin 1 only by the absence of the C30 carbomethoxy group (on the C13 enoate of the B-ring), has been prepared by total synthesis. Biological assays reveal a crucial role for substitution in the bryostatin 1 A-ring in conferring those responses which are characteristic of bryostatin 1 and distinct from those observed with PMA.

Bryostatin 1, like the phorbol esters, binds to and activates protein kinase C (PKC) but paradoxically antagonizes many but not all phorbol ester responses. Previously, we have compared patterns of biological response to bryostatin 1, phorbol ester, and the bryostatin 1 derivative Merle 23 in two human cancer cell lines, LNCaP and U937. Bryostatin 1 fails to induce a typical phorbol ester biological response in either cell line, whereas Merle 23 resembles phorbol ester in the U937 cells and bryostatin 1 in the LNCaP cells. Here, we have compared the pattern of their transcriptional response in both cell lines. We examined by qPCR the transcriptional response as a function of dose and time for a series of genes regulated by PKCs. In both cell lines bryostatin 1 differed primarily from phorbol ester in having a shorter duration of transcriptional modulation. This was not due to bryostatin 1 instability, since bryostatin 1 suppressed the phorbol ester response. In both cell lines Merle 23 induced a pattern of transcription largely like that of phorbol ester although with a modest reduction at later times in the LNCaP cells, suggesting that the difference in biological response of the two cell lines to Merle 23 lies downstream of this transcriptional regulation. For a series of bryostatins and analogues which ranged from bryostatin 1-like to phorbol ester-like in activity on the U937 cells, the duration of transcriptional response correlated with the pattern of biological activity, suggesting that this may provide a robust platform for structure activity analysis.

Antibody drug conjugates (ADCs) can undergo in vivo biotransformation (e.g., payload metabolism, deconjugation) leading to reduced or complete loss of activity. The location/site of conjugation of payload-linker can have an effect on ADC stability and hence needs to be carefully optimized. Affinity capture LC–MS of intact ADCs or ADC subfragments has been extensively used to evaluate ADC biotransformation. However, the current methods have certain limitations such as the requirement of specific capture reagents, limited mass resolution of low mass change metabolites, low sensitivity, and use of capillary or nanoflow LC–MS. To address these challenges, we developed a generic affinity capture LC–MS assay that can be utilized to evaluate the biotransformation of any site-specific ADC independent of antibody type and site of conjugation (Fab and Fc) in preclinical studies. The method involves a combination of some or all of these steps: (1) “mono capture” or “dual capture” of ADCs from serum with streptavidin magnetic beads coated with a generic biotinylated antihuman capture reagent, (2) “on-bead” digestion with IdeS and/or PNGase F, and (3) reduction of interchain disulfide bonds to generate ∼25 kDa ADC subfragments, which are finally analyzed by LC–HRMS on a TOF mass spectrometer. The advantages of this method are that it can be performed using commercially available generic reagents and requires sample preparation time of less than 7 h. Furthermore, by reducing the size of intact ADC (∼150 kDa) to subfragments (∼25 kDa), the identification of conjugated payload and its metabolites can be achieved with excellent sensitivity and resolution (hydrolysis and other small mass change metabolites). This method was successfully applied to evaluate the in vitro and in vivo biotransformation of ADCs conjugated at different sites (LC, HC-Fab, and HC-Fc) with various classes of payload-linkers.

The total syntheses of dihydrolysergic acid and dihydrolysergol are detailed based on a Pd(0)-catalyzed intramolecular Larock indole cyclization for the preparation of the embedded tricyclic indole (ABC ring system) and a subsequent powerful inverse electron demand Diels–Alder reaction of 5-carbomethoxy-1,2,3-triazine with a ketone-derived enamine for the introduction of a functionalized pyridine, serving as the precursor for a remarkably diastereoselective reduction to the N-methylpiperidine D-ring. By design, the use of the same ketone-derived enamine and a set of related complementary heterocyclic azadiene [4 + 2] cycloaddition reactions permitted the late stage divergent preparation of a series of alternative heterocyclic derivatives not readily accessible by more conventional approaches.