Re: Chemistry

[will johnston <johnston@xxxxxxxxxxxxxxxxxx>]

At 08:15 PM 5/2/97 -0400, you wrote:
>Chemistry: (This won't add the slightest bit of help or info about
>PD, just a little fun to share with the technically minded.) From
>time to time I wondered about the loose and interchangeable use of
>the terms DOPA, L-DOPA, Levodopa, and Dopamine- so I decided to look
>up the definitions. The books don't all agree exactly, but I think I
>have a handle on it that is adequate for my degree of interest.
>Names of compounds are often chosen to tell a little about the
>chemcal's composition. DOPA is an acronym, or shorthand, for
>DihydrOxyPhenylAlanine, as depicted below. The diagrams are another
>kind of shorthand, where chemists can recognize familiar groups and
>see how they go together. You need to recall from freshman chemistry
>how compound molecules are made of atoms connected by something
>called valence bonds, of which each element has a characteristic
>number: Hydrogen 1, Oxygen 2, Nitrogen (usually) 3, and Carbon 4.
>In DOPA, the hydroxyl group is water, H2O, minus a hydrogen. The
>phenyl is based on the benzene hexagon, C6H6, and Alanine, itself
>an amino acid when complete, is the group on the right. DOPA
>becomes Dopamine when the C-O-OH part of the alanine group is
>replaced by a single hydrogen atom. Levodopa refers to the fact that
>the DOPA molecule isn't flat like its diagram, but has a three=
>dimensional aspect that permits more than one shape. When you look
>at a solution of DOPA through a Polaroid filter, you find that one
>of its forms twists the polarization to the left, or "levo". The
>Different forms of a compound may have identical composition but
>quite distinct chemical properties. The best analog I can think of
>for right- or left-handedness is in a pair of dice. If you obey the
>convention that marks on opposite sides of each cube must add up to
>7, and look at a corner so you can see 1, 2, and 3, there are two
>possible arrangements: clockwise and counterclockwise. Something
>like that happens in many chemical compounds.
>
>             H                         H   H     H
>             |                         |   |    /
>        H    C   H                 H---C---C---N---H
>         \ // \ /                      |   |
>          C    C                       H   C--O--H
>          |    ||                          \\
>          C    C                            O
>         / \\ / \
>        H    C   H                     Alanine
>             |
>             H
>
>          Benzene
>
>            H                               H
>            |                               |
>    H--O    C     H   H     H       H--O    C     H   H     H
>        \ // \    |   |    /            \ // \    |   |    /
>         C    C---C---C---N--H           C    C---C---C---N--H
>         |    ||  |   |                  |    ||  |   |
>         C    C   H   C--O--H            C    C   H   H
>        / \\ / \      \\                / \\ / \
>    H--O    C   H      O            H--O    C   H
>(Dihydroxy) |      (Alanine)                |
>            H                               H
>        (Phenyl)      (Carboxyl)
>
>  DOPA = DihydrOxyPhenylAlanine         Dopamine
>        (Levodopa)
>
>
>
>
>J. R. Bruman (818) 789-3694
>3527 Cody Road
>Sherman Oaks CA 91403
>


J.R.

For an interesting look at the problem, see William S. Knowles 'ASYMMETRIC
HYDROGENATION'in the Accounts of Chemical Research [1983] 16,106-112. It's
tough reading but on topic. Knowles is or was an aggie chem researcher with
Monsanto. I don't know him. He got his PhD at Columba in 1942...and that's a
long time back for a graduate degree.

Will
And here's to long "ons" and short "offs"

WILL JOHNSTON   4049 OAKLAND SCHOOL ROAD
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