Look what I found while buying the stuff for my eugenol experiments...
I used TFSE for kaffeesaure, Kaffeesäure and coffee combined with acid, and didn't find anything that looks like this, so I thought I should mention it.

This is 'kaffeesäure' or 'coffee acid':
https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000511810-caffeesaure.gif" target="_blank" title="View this image">

I first read about it here:

http://www.fslemi.uni-bonn.de/gewuerze/html/stralsklasse/sel.html

References are here

http://www.paracelsus.de/heilv/natur_177.html

and here

http://www.g-netz.de/Health_Center/heilpflanzen/zzwirkstoffe/phenolsaeuren.shtml#phenolsaeuren

.
The latter also has a list of sources (other than the obvious considering the name).

Other names appear to be 3,4-Dihydroxyzimtsäure (= 3,4-dihydroxycinnamaldehyde) and 3-O-Caffeoyl-D-chinasäure, but I haven't found it in the 84th edition of the CRC.
Searching on the web it appears to be freely availabe in pure form(5 g = 19 euros at the first site I found it). Take note: you have to type the a-umlaut (ä) correctly in order to find anything in Google.

Am I on to something here, or am I just really showing my newbee status in an almost obscene way?  

The real question is: is it economically and practically feasible to change the carboxyl group to a methyl group (either before or after methylenation of the hydroxyl groups on the road to safrole, as described

here

(https://www.thevespiary.org/rhodium/Rhodium/chemistry/methylenation.html).

The moving of the double bond can of course be found

here

(https://www.thevespiary.org/rhodium/Rhodium/chemistry/isomerizafrole.html).

I don't have the knowledge to answer this question yet, hope you can help.

caffeic acid.

Ahaaaaa!

Thanks

It's fun though, putting the pieces together for myself, a great learning experience!

Perhaps we at the hive would have a use for some 3,4-dihydroxybenzaldehyde....?

Ozone, or perhaps KMnO4 under certain conditions?

do a search:

Post 122772

(dormouse: "MDA from Coffee  -Wizard X", Serious Chemistry)

Post 323392

(mellow: "MDP2P from waste vegetation?", Novel Discourse)

You also have the trouble that you end up with a carboxylic acid. To get that group converting to something useful, you need serious chemistry. When you have access to those things, why not order a less troublesome precursor? :-)

I knew it was only a matter of time!

This is definitely a synth whose time has come.
Changing a carboxylic group isn't as serious as
working CH₂I₂.  Nasty chemical there,
of course SWIM likes H₂S and Chloroacetone ...
let the fun begin.

Occassionally an old idea gets brought up in
a new thread and people who haven't seen it
before take a look.

Reducing carboxylic acids to alkanes is rather impractical. How about oxidising 3,4-dihydroxycinnamic acid to protocatechualdehyde with modified permanganate (as ning suggested), followed by methylenation? It may be best to first methylenate to 3,4-methylenedioxycinnamic acid, which would give piperonal directly upon oxidation. The following article deals with the oxidation of plain cinnamic acid to benzaldehyde with permanganate on alumina:

Heterogeneous Permanganate Oxidations. 5. The Preparation of Aldehydes by Oxidative Cleavage of Carbon-Carbon Double Bonds
Donald G. Lee,^* Tao Chen, and Zhao Wang
J. Org. Chem. 1993, 58, 2918-2919

https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000511810-JOC_58_Permanganate_oxidation_of_alkenes_to_aldehydes.pdf" target="_blank" title="Download this file">

Also see

Cleavage of alkenes to aldehydes using potassium permanganate

(https://www.thevespiary.org/rhodium/Rhodium/chemistry/alkene2aldehyde.kmno4-thf.html).