Access scheme

The protic catalytic conditions are also compatible with trapping of the radicals formed after cyclization with acrylates or acrylonitriles prior to their reduction with Cp2TiCl . In this manner highly substituted alkenes for the potential preparation of modified steroids can be accessed (Scheme 19) [97]. 

By combining the benefits of Pd(II) and Ti(III) chemistry, syntheses of y-dioxygenated terpenoids, such as rostratone could be readily accessed (Scheme 27) [113]. 

These initial forays verified the utility of the process and provided mechanistic information which set the stage for further exploration into the scope of the process. Successful reactions with a variety of substrates demonstrated the generality of the process, with 6- and 7-membered cyclic enol ethers being most accessible (Scheme 19). Preservation of the trisubstituted olefin present in the complex substrate 132 indicates the chemoselective nature of the process [34a]. 

There can be a variety of drawbacks to the direct access scheme making it more difficult to guarantee abstract object invariants and exposing more of the internal design decisions than necessary. Each of them applies only in certain circumstances. 

You need not design the external objects to know which constituent to connect to. In the direct access scheme, refining our object also means designing the externals to work with our organization. 

Special access scheme www.tga.gov.au/docs/ html/sasinfo.htm... 

By the same method, the asymmetrical compounds 196a and 196b (from alkenes 195a and 195b), the related dilithiated compounds of tetrakis(dimethylsilyl)ethylene (197) and the tetrasilabicyclopentylidene 198 were accessible (Scheme 66) . The results of the X-ray structural analyses are shown (Figures 23 and 24). 

In poly[2,5-bis(3,4-ethylene-dioxy-2-thienyl)pyridine], a copolymer of thiophene and pyridine in a 2 1 ratio, the effective HOMO and LUMO energy levels of the ir-system are controlled in such a way that both p-doped and n-doped states are accessible (Scheme 9) [43]. The thin fdms display multicolor... 

The Dess-Martin periodinane 8 is also able to oxidize aromatic compounds to the corresponding quinones. The presence of water is important and, starting from anilides 42 substituted in the 2-position, the rare class of ortho-imido-quinones 43 is accessible, Scheme 21. It has been shown that compounds of type 43 are interesting building blocks and can lead to polycyclic molecules of diverse molecular architecture [95,96]. They can undergo subsequent Diels-Alder reactions and intramolecular versions have been used for a rapid access to natural products and for synthesis of scaffolds for further manipulation.para-Quinones 45 are also easily accessible, however, only in modest yields by reacting 4-sub-stituted anilines 44 under the same reaction conditions, Scheme 21 [97]. 

Deprotonation followed by addition of an electrophile, if needed combined with application of protecting groups, makes a great number of regi-oselectively substituted 1,2,3-triazole 1-oxides 448 accessible (Scheme 146). 

PDB-ID Codes. The structure record accessioning scheme of the Protein Data Bank is a unique four-character alphanumeric code, called a PDB-ID or PDB code. This scheme uses the digits 0 to 9 and the uppercase letters A to Z. This allows for over 1.3 million possible combinations and entries. Many older records have mnemonic names that make the structures easier to remember, such as 3INS, the record for insulin shown earlier. A different method is now being used to assign PDB-IDs, with the use of mnemonics apparently being abandoned. 

Nanaomycin D (48) and its enantiomer kalafungin (49) were both accessible (Scheme 9) from the enone (50), itself derived from L-... 

A diastereo- and enantioselective Michael addition combined with a Darzens condensation reaction can be used to form two products of interest in the field of medicinal and natural products chemistry [60]. Additionally, depending on the workup conditions, an optically active epoxycyclohexanone, 92, can be prepared through an Sf 2 reaction, or the ElcB reaction pathway to 91 can be accessed (Scheme 7.17). In the early stages of the proposed mechanism, a planar iminium ion is suggested between the 2-[bis(3,5-bistrifluoromethylphenyl) trimethylsilany-loxymethyljpyrrolidine 61 and the aldehyde moiety of compound 88, which is subsequently attacked by the P-ketoester 89. For the synthesis of the epoxide, a... 

Last year, Alexanian and Bloome described a palladium-catalyzed carbonylative Heck-type cyclization of alkyl halides [32]. The treatment of a range of primary and secondary alkyl iodides in the presence of a palladium catalyst under CO pressure yielded a variety of synthetically versatile enone products. This novel palladium-catalyzed Heck-type cyclization is a rare example where inactivated alkyl halides with -hydrogens are involved. Various substituted alkenes were well tolerated, and mono- as well as bicyclic carbocycles are easily accessed (Scheme 7.13). 

Some special memory structures do not follow the general accessing scheme of using an address. Two of the most frequently used are content addressable memory (CAM), and first-in-first-out (FIFO) memory. Another type of memory device, which accepts multiple addresses and produces several results at different ports, is called multiport memory. There is also a type of memory that can be written in parallel, but is read serially. It is referred to as video RAM or VDRAM since they are used primarily in graphic display applications. We will discuss these in more detail later. 

If a perfect memory property could be realized, the refreshing process would not be necessary. Only by a partial access scheme could a higji contrast ratio be obtained. On the other hand, in the case of SSFLCs with a poor memory property, the refreshing process must be carried out frequently, and the number of scanning lines would be limited. For SSFLCs, memory property determines both the number of scanning lines and the contrast ratio. 

Inversion during formation of the Ti -allyl complex is not always observed. For the tricyclic compound 9.119, the endo face is sterically blocked, and only the exo face is accessible (Scheme 9.37). It was observed that only the exo isomer reacted with a malonate nucleophile in the presence of a molybdenum catalyst. ... 

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